mysql续集(查询部分)

mysql查询部分,从基础的查询到关键字,where子句,group by, order by, limit ,having,子查询分为from子查询和where子查询,左连接和右连接,内连接的连表查询.一些题目的练习,希望能够越学越多,加油............................................................................................................凑字数.

表结构准备:

create table goods (
  goods_id mediumint(8) unsigned primary key auto_increment,
  goods_name varchar(120) not null default '',
  cat_id smallint(5) unsigned not null default '0',
  brand_id smallint(5) unsigned not null default '0',
  goods_sn char(15) not null default '',
  goods_number smallint(5) unsigned not null default '0',
  shop_price decimal(10,2) unsigned not null default '0.00',
  market_price decimal(10,2) unsigned not null default '0.00',
  click_count int(10) unsigned not null default '0'
) engine=myisam default charset=utf8;
insert into `goods` values (1,'kd876',4,8,'ecs000000',1,1388.00,1665.60,9),
(4,'诺基亚n85原装充电器',8,1,'ecs000004',17,58.00,69.60,0),
(3,'诺基亚原装5800耳机',8,1,'ecs000002',24,68.00,81.60,3),
(5,'索爱原装m2卡读卡器',11,7,'ecs000005',8,20.00,24.00,3),
(6,'胜创kingmax内存卡',11,0,'ecs000006',15,42.00,50.40,0),
(7,'诺基亚n85原装立体声耳机hs-82',8,1,'ecs000007',20,100.00,120.00,0),
(8,'飞利浦9@9v',3,4,'ecs000008',1,399.00,478.79,10),
(9,'诺基亚e66',3,1,'ecs000009',4,2298.00,2757.60,20),
(10,'索爱c702c',3,7,'ecs000010',7,1328.00,1593.60,11),
(11,'索爱c702c',3,7,'ecs000011',1,1300.00,0.00,0),
(12,'摩托罗拉a810',3,2,'ecs000012',8,983.00,1179.60,13),
(13,'诺基亚5320 xpressmusic',3,1,'ecs000013',8,1311.00,1573.20,13),
(14,'诺基亚5800xm',4,1,'ecs000014',1,2625.00,3150.00,6),
(15,'摩托罗拉a810',3,2,'ecs000015',3,788.00,945.60,8),
(16,'恒基伟业g101',2,11,'ecs000016',0,823.33,988.00,3),
(17,'夏新n7',3,5,'ecs000017',1,2300.00,2760.00,2),
(18,'夏新t5',4,5,'ecs000018',1,2878.00,3453.60,0),
(19,'三星sgh-f258',3,6,'ecs000019',12,858.00,1029.60,7),
(20,'三星bc01',3,6,'ecs000020',12,280.00,336.00,14),
(21,'金立 a30',3,10,'ecs000021',40,2000.00,2400.00,4),
(22,'多普达touch hd',3,3,'ecs000022',1,5999.00,7198.80,16),
(23,'诺基亚n96',5,1,'ecs000023',8,3700.00,4440.00,17),
(24,'p806',3,9,'ecs000024',100,2000.00,2400.00,35),
(25,'小灵通/固话50元充值卡',13,0,'ecs000025',2,48.00,57.59,0),
(26,'小灵通/固话20元充值卡',13,0,'ecs000026',2,19.00,22.80,0),
(27,'联通100元充值卡',15,0,'ecs000027',2,95.00,100.00,0),
(28,'联通50元充值卡',15,0,'ecs000028',0,45.00,50.00,0),
(29,'移动100元充值卡',14,0,'ecs000029',0,90.00,0.00,0),
(30,'移动20元充值卡',14,0,'ecs000030',9,18.00,21.00,1),
(31,'摩托罗拉e8 ',3,2,'ecs000031',1,1337.00,1604.39,5),
(32,'诺基亚n85',3,1,'ecs000032',4,3010.00,3612.00,9);
create table category (
cat_id smallint unsigned auto_increment primary key,
cat_name varchar(90) not null default '',
parent_id smallint unsigned
)engine myisam charset utf8;
INSERT INTO `category` VALUES
(1,'手机类型',0),
(2,'CDMA手机',1),
(3,'GSM手机',1),
(4,'3G手机',1),
(5,'双模手机',1),
(6,'手机配件',0),
(7,'充电器',6),
(8,'耳机',6),
(9,'电池',6),
(11,'读卡器和内存卡',6),
(12,'充值卡',0),
(13,'小灵通/固话充值卡',12),
(14,'移动手机充值卡',12),
(15,'联通手机充值卡',12);
CREATE TABLE `result` (
  `name` varchar(20) DEFAULT NULL,
  `subject` varchar(20) DEFAULT NULL,
  `score` tinyint(4) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
insert into result
values
('张三','数学',90),
('张三','语文',50),
('张三','地理',40),
('李四','语文',55),
('李四','政治',45),
('王五','政治',30);
create table a (
id char(1),
num int
)engine myisam charset utf8;
insert into a values ('a',5),('b',10),('c',15),('d',10);
create table b (
id char(1),
num int
)engine myisam charset utf8;
insert into b values ('b',5),('c',15),('d',20),('e',99);
create table m(
     mid int,
     hid int,
     gid int,
     mres varchar(10),
     matime date
)engine myisam charset utf8;
create table t (
     tid int,
     tname varchar(20)
)engine myisam charset utf8;
insert into m
     values
     (1,1,2,'2:0','2006-05-21'),
     (2,2,3,'1:2','2006-06-21'),
     (3,3,1,'2:5','2006-06-25'),
     (4,2,1,'3:2','2006-07-21');
insert into t
     values
     (1,'国安'),
     (2,'申花'),
     (3,'布尔联队');
create table mian ( num int) engine myisam;
insert into mian values
(3),
(12),
(15),
(25),
(23),
(29),
(34),
(37),
(32);
create table user (
uid int primary key auto_increment,
name varchar(20) not null default '',
age smallint unsigned not null default 0
) engine myisam charset utf8;
create table boy (
    hid char(1),
     bname varchar(20)
)engine myisam charset utf8;
insert into boy (bname,hid)
     values
     ('屌丝','A'),
     ('杨过','B'),
     ('陈冠希','C');
create table girl (
    hid char(1),
     gname varchar(20)
     )engine myisam charset utf8;
insert into girl(gname,hid)
     values
     ('小龙女','B'),
     ('张柏芝','C'),
     ('死宅女','D');

mysql> select goods_name,goods_id, concat("HTC",substring(goods_name,4)) as name from goods where goods_name like "诺基亚%";
+----------------------------------------+----------+----------------------------------+
| goods_name | goods_id | name |
+----------------------------------------+----------+----------------------------------+
| 诺基亚n85原装充电器 | 4 | HTCn85原装充电器 |
| 诺基亚原装5800耳机 | 3 | HTC原装5800耳机 |
| 诺基亚n85原装立体声耳机hs-82 | 7 | HTCn85原装立体声耳机hs-82 |
| 诺基亚e66 | 9 | HTCe66 |
| 诺基亚5320 xpressmusic | 13 | HTC5320 xpressmusic |
| 诺基亚5800xm | 14 | HTC5800xm |
| 诺基亚n96 | 23 | HTCn96 |
| 诺基亚n85 | 32 | HTCn85 |
+----------------------------------------+----------+----------------------------------+
8 rows in set (0.00 sec)

mysql> select * from mian
-> ;
+------+
| num |
+------+
| 3 |
| 12 |
| 15 |
| 20 |
| 20 |
| 20 |
| 30 |
| 30 |
| 30 |
+------+
9 rows in set (0.00 sec)

mysql> #取出第三个栏目下价格小于1000或者大于3000 同时点击量大于5的商品
mysql> select goods_id ,goods_name, shop_price,cat_id,click_count from goods where cat_id=3 and (shop_price<1000 || shop_price>3000) and click_count >=5 ; 
+----------+-------------------+------------+--------+-------------+
| goods_id | goods_name | shop_price | cat_id | click_count |
+----------+-------------------+------------+--------+-------------+
| 8 | 飞利浦9@9v | 399.00 | 3 | 10 |
| 12 | 摩托罗拉a810 | 983.00 | 3 | 13 |
| 15 | 摩托罗拉a810 | 788.00 | 3 | 8 |
| 19 | 三星sgh-f258 | 858.00 | 3 | 7 |
| 20 | 三星bc01 | 280.00 | 3 | 14 |
| 22 | 多普达touch hd | 5999.00 | 3 | 16 |
| 32 | 诺基亚n85 | 3010.00 | 3 | 9 |
+----------+-------------------+------------+--------+-------------+
7 rows in set (0.00 sec)

mysql> #最贵的商品的价格
mysql> select max(shop_price) from goods;
+-----------------+
| max(shop_price) |
+-----------------+
| 5999.00 |
+-----------------+
1 row in set (0.06 sec)

mysql> #查询最便宜的商品的价格
mysql> select min(shop_price) from goods ;
+-----------------+
| min(shop_price) |
+-----------------+
| 18.00 |
+-----------------+
1 row in set (0.00 sec)

mysql> #查出最旧的商品
mysql> select min(goods_id) from goods;
+---------------+
| min(goods_id) |
+---------------+
| 1 |
+---------------+
1 row in set (0.10 sec)

mysql> #goods_number是库存量
mysql> select sum(goods_number) from goods
-> ;
+-------------------+
| sum(goods_number) |
+-------------------+
| 313 |
+-------------------+
1 row in set (0.00 sec)

mysql> #查看自己店里的商品的平均价格

mysql> select avg(shop_price) from goods;
+-----------------+
| avg(shop_price) |
+-----------------+
| 1232.526774 |
+-----------------+
1 row in set (0.00 sec)

mysql> #统计多少种商品
mysql> select count(*) from goods;
+----------+
| count(*) |
+----------+
| 31 |
+----------+
1 row in set (0.00 sec)

mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| girl |
| goods |
| m |
| mian |
| result |
| t |
| user |
+------------------+
11 rows in set (0.17 sec)

mysql> select * from t;
+------+--------------+
| tid | tname |
+------+--------------+
| 1 | 国安 |
| 2 | 申花 |
| 3 | 布尔联队 |
+------+--------------+
3 rows in set (0.06 sec)

mysql> #select count(*) from 表名,表示查询的是绝对的行数,哪怕某一行所有字段全为null的时候也能计算在内,
mysql> #而select count(字段) from 表名 查询的是该列不为null的所有行的行数
mysql> #用count(*)和count(1) 那个好,对于myisamm的表咩有区别,这种引擎计数器在维护,innodb的用count(*))直接读行数,效率很低
mysql> #计算第三个栏目下所有商品的库存量之和
mysql> select sum(goods_number) from goods where cat_id =3;
+-------------------+
| sum(goods_number) |
+-------------------+
| 203 |
+-------------------+
1 row in set (0.00 sec)

mysql> #计算每个栏目下的库存量之和
mysql> select cat_id, sum(goods_number) from goods group by cat_id ;
+--------+-------------------+
| cat_id | sum(goods_number) |
+--------+-------------------+
| 4 | 3 |
| 8 | 61 |
| 11 | 23 |
| 3 | 203 |
| 2 | 0 |
| 5 | 8 |
| 13 | 4 |
| 15 | 2 |
| 14 | 9 |
+--------+-------------------+
9 rows in set (0.05 sec)

mysql> #having 筛选
mysql> #查询每种商品积压的货款
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| bookstore |
| clouddb01 |
| clouddb02 |
| clouddb03 |
| information_schema |
| mydb |
| mysql |
| performance_schema |
| shop |
| ssm_crud |
| struts |
| student |
| sys |
| test |
| test01 |
+--------------------+
15 rows in set (0.00 sec)

mysql> #查询每种商品积压的货款
mysql> select market_price,shop_price, market_price-shop_price as discount from goods where 1 having discount >200;
ERROR 1046 (3D000): No database selected
mysql> use test01;
Database changed

mysql> #查询每种商品积压的货款
mysql> #提示: 商品的库存量*价格

mysql> select goods_id ,shop_price,goods_number*shop_price as hk from goods;
+----------+------------+-----------+
| goods_id | shop_price | hk |
+----------+------------+-----------+
| 1 | 1388.00 | 1388.00 |
| 4 | 58.00 | 986.00 |
| 3 | 68.00 | 1632.00 |
| 5 | 20.00 | 160.00 |
| 6 | 42.00 | 630.00 |
| 7 | 100.00 | 2000.00 |
| 8 | 399.00 | 399.00 |
| 9 | 2298.00 | 9192.00 |
| 10 | 1328.00 | 9296.00 |
| 11 | 1300.00 | 1300.00 |
| 12 | 983.00 | 7864.00 |
| 13 | 1311.00 | 10488.00 |
| 14 | 2625.00 | 2625.00 |
| 15 | 788.00 | 2364.00 |
| 16 | 823.33 | 0.00 |
| 17 | 2300.00 | 2300.00 |
| 18 | 2878.00 | 2878.00 |
| 19 | 858.00 | 10296.00 |
| 20 | 280.00 | 3360.00 |
| 21 | 2000.00 | 80000.00 |
| 22 | 5999.00 | 5999.00 |
| 23 | 3700.00 | 29600.00 |
| 24 | 2000.00 | 200000.00 |
| 25 | 48.00 | 96.00 |
| 26 | 19.00 | 38.00 |
| 27 | 95.00 | 190.00 |
| 28 | 45.00 | 0.00 |
| 29 | 90.00 | 0.00 |
| 30 | 18.00 | 162.00 |
| 31 | 1337.00 | 1337.00 |
| 32 | 3010.00 | 12040.00 |
+----------+------------+-----------+
31 rows in set (0.00 sec)

mysql> #查询该店积压的总货款
mysql> select goods_number ,sum(goods_number*shop_price) as sum from goods;
+--------------+-----------+
| goods_number | sum |
+--------------+-----------+
| 1 | 398620.00 |
+--------------+-----------+
1 row in set (0.07 sec)

mysql> select sum(goods_number*shop_price) as sum from goods;
+-----------+
| sum |
+-----------+
| 398620.00 |
+-----------+
1 row in set (0.00 sec)

mysql> #查询每个栏目下积压的k货款
mysql> select cat_id, sum(goods_number*shop_price) as sum from goods group by cat_id;
+--------+-----------+
| cat_id | sum |
+--------+-----------+
| 4 | 6891.00 |
| 8 | 4618.00 |
| 11 | 790.00 |
| 3 | 356235.00 |
| 2 | 0.00 |
| 5 | 29600.00 |
| 13 | 134.00 |
| 15 | 190.00 |
| 14 | 162.00 |
+--------+-----------+
9 rows in set (0.03 sec)

mysql> #查询栏目的积压货款金额,且查出挤压金额超出20000的货款
mysql> select cat_id, sum(goods_number*shop_price) as sum from goods group by cat_id having sum>20000;
+--------+-----------+
| cat_id | sum |
+--------+-----------+
| 3 | 356235.00 |
| 5 | 29600.00 |
+--------+-----------+
2 rows in set (0.00 sec)

mysql> #查询本店市场价与本店价省的钱,且筛选出省钱200以上的商品
mysql> select goods_name, market_price-shop_price as discount from goods having discount>200;
ERROR 1690 (22003): DECIMAL UNSIGNED value is out of range in '(`test01`.`goods`.`market_price` - `test01`.`goods`.`shop_price`)'
mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| girl |
| goods |
| m |
| mian |
| result |
| t |
| user |
+------------------+
11 rows in set (0.14 sec)

mysql> select * from result;
+--------+---------+-------+
| name | subject | score |
+--------+---------+-------+
| 张三 | 数学 | 90 |
| 张三 | 语文 | 50 |
| 张三 | 地理 | 40 |
| 李四 | 语文 | 55 |
| 李四 | 政治 | 45 |
| 王五 | 政治 | 30 |
+--------+---------+-------+
6 rows in set (0.07 sec)

mysql> #查询出两门及两门以上不及格者的平均成绩
mysql> select avg(score) as average ,subject from result where subject>=2 group by name having average<60;
Empty set, 6 warnings (0.00 sec)

mysql> select avg(score) as average ,subject from result group by name;
+---------+---------+
| average | subject |
+---------+---------+
| 60.0000 | 数学 |
| 50.0000 | 语文 |
| 30.0000 | 政治 |
+---------+---------+
3 rows in set (0.00 sec)

mysql> select avg(score) as average ,name from result group by name;
+---------+--------+
| average | name |
+---------+--------+
| 60.0000 | 张三 |
| 50.0000 | 李四 |
| 30.0000 | 王五 |
+---------+--------+
3 rows in set (0.00 sec)


mysql> select avg(score) as average ,name from result where 1 group by name;
+---------+--------+
| average | name |
+---------+--------+
| 60.0000 | 张三 |
| 50.0000 | 李四 |
| 30.0000 | 王五 |
+---------+--------+
3 rows in set (0.00 sec)

mysql> select avg(score) as average ,name from result where 1 group by name having average<60 ;
+---------+--------+
| average | name |
+---------+--------+
| 50.0000 | 李四 |
| 30.0000 | 王五 |
+---------+--------+
2 rows in set (0.00 sec)


mysql> select avg(score) as average ,name from result where score<60 group by name having avg(average) ;
Empty set (0.00 sec)

mysql> select avg(score<60) as average ,name from result where 1 group by name having avg(average) ;
Empty set (0.00 sec)

mysql> select avg(score<60) as average ,name from result where 1 group by name ;
+---------+--------+
| average | name |
+---------+--------+
| 0.6667 | 张三 |
| 1.0000 | 李四 |
| 1.0000 | 王五 |
+---------+--------+
3 rows in set (0.00 sec)

mysql> select avg(score) as average ,name from result where score<60 group by name ;
+---------+--------+
| average | name |
+---------+--------+
| 45.0000 | 张三 |
| 50.0000 | 李四 |
| 30.0000 | 王五 |
+---------+--------+
3 rows in set (0.00 sec)

mysql> select avg(score) as average ,name from result where subject>=2 group by name ;
Empty set, 6 warnings (0.00 sec)

mysql> select avg(score) as average ,name,count(subject) from result where score<60 group by name ;
+---------+--------+----------------+
| average | name | count(subject) |
+---------+--------+----------------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
| 30.0000 | 王五 | 1 |
+---------+--------+----------------+
3 rows in set (0.00 sec)


mysql> select avg(score) as average ,name,count(subject) as subject from result where score<60 group by name having subject>=2 ;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.00 sec)


mysql> select avg(score) as average ,name,count(subject) as subject from result where score<60 group by name having subject>=2 and avg(average);
Empty set (0.00 sec)


mysql> select avg(score) as average ,name,count(subject)>=2 as subject from result where score<60 group by name having avg(average);
Empty set (0.00 sec)


mysql> select avg(score) as average ,name,count(subject) as subject from result where score<60 group by name having subject>=2;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.00 sec)


mysql> select avg(score) as average ,name from result where score<60 group by name ;
+---------+--------+
| average | name |
+---------+--------+
| 45.0000 | 张三 |
| 50.0000 | 李四 |
| 30.0000 | 王五 |
+---------+--------+
3 rows in set (0.00 sec)

mysql> select avg(score) as average ,name,count(subject) from result where score<60 group by name ;
+---------+--------+----------------+
| average | name | count(subject) |
+---------+--------+----------------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
| 30.0000 | 王五 | 1 |
+---------+--------+----------------+
3 rows in set (0.00 sec)

mysql> select avg(score) as average ,name,count(subject)>=2 from result where score<60 group by name ;
+---------+--------+-------------------+
| average | name | count(subject)>=2 |
+---------+--------+-------------------+
| 45.0000 | 张三 | 1 |
| 50.0000 | 李四 | 1 |
| 30.0000 | 王五 | 0 |
+---------+--------+-------------------+
3 rows in set (0.00 sec)


mysql> select avg(score) as average ,name,count(subject)>=2 from result where score<60 group by name ;
+---------+--------+-------------------+
| average | name | count(subject)>=2 |
+---------+--------+-------------------+
| 45.0000 | 张三 | 1 |
| 50.0000 | 李四 | 1 |
| 30.0000 | 王五 | 0 |
+---------+--------+-------------------+
3 rows in set (0.00 sec)


mysql> select avg(score) as average ,name,count(subject) from result where score<60 group by name ;
+---------+--------+----------------+
| average | name | count(subject) |
+---------+--------+----------------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
| 30.0000 | 王五 | 1 |
+---------+--------+----------------+
3 rows in set (0.00 sec)


mysql> select avg(score) as average ,name from result where score<60 and subject>=2 group by name ;
Empty set, 5 warnings (0.00 sec)

mysql> select avg(score) as average ,name, count(subject) from result where score<60 and subject>=2 group by name ;
Empty set, 5 warnings (0.00 sec)

mysql> select avg(score) as average ,name, count(subject) from result where score<60 group by name ;
+---------+--------+----------------+
| average | name | count(subject) |
+---------+--------+----------------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
| 30.0000 | 王五 | 1 |
+---------+--------+----------------+
3 rows in set (0.00 sec)

mysql> select avg(score) as average ,name, count(subject) as subject from result where score<60 group by name having subject>=2 ;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.00 sec)

mysql> use test01
Database changed
mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| girl |
| goods |
| m |
| mian |
| result |
| t |
| user |
+------------------+
11 rows in set (0.42 sec)

mysql> select avg(score) as average ,name, count(subject) as subject from result where score<60 group by name having subject>=2 ;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.14 sec)

mysql> insert into resule values("赵六","语文",100),
-> ("赵六","数学",99),
-> ("赵六","英语",98);
ERROR 1146 (42S02): Table 'test01.resule' doesn't exist
mysql> insert into result values("赵六","语文",100),
-> ("赵六","数学",99),
-> ("赵六","英语",98);
Query OK, 3 rows affected (0.19 sec)
Records: 3 Duplicates: 0 Warnings: 0

mysql> select * from result;
+--------+---------+-------+
| name | subject | score |
+--------+---------+-------+
| 张三 | 数学 | 90 |
| 张三 | 语文 | 50 |
| 张三 | 地理 | 40 |
| 李四 | 语文 | 55 |
| 李四 | 政治 | 45 |
| 王五 | 政治 | 30 |
| 赵六 | 语文 | 100 |
| 赵六 | 数学 | 99 |
| 赵六 | 英语 | 98 |
+--------+---------+-------+
9 rows in set (0.00 sec)

mysql> select avg(score) as average ,name, count(subject) as subject from result where score<60 group by name having subject>=2;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 45.0000 | 张三 | 2 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.00 sec)

mysql> insert into result values("张三","英语",34);
Query OK, 1 row affected (0.05 sec)

mysql> select avg(score) as average ,name, count(subject) as subject from result where score<60 group by name having subject>=2;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 41.3333 | 张三 | 3 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.00 sec)

mysql> select avg(score) as average ,name, sum(score<60) as subject from result group by name having subject>=2;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 53.5000 | 张三 | 3 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.00 sec)

mysql> select avg(score) as average ,name, sum(score<60) as subject from result group by name having subject>=2 order by average;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 50.0000 | 李四 | 2 |
| 53.5000 | 张三 | 3 |
+---------+--------+---------+
2 rows in set (0.00 sec)

mysql> select avg(score) as average ,name, sum(score<60) as subject from result group by name having subject>=2 order by desc average;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'desc average' at line 1
mysql> select avg(score) as average ,name, sum(score<60) as subject from result group by name having subject>=2 order by average desc;
+---------+--------+---------+
| average | name | subject |
+---------+--------+---------+
| 53.5000 | 张三 | 3 |
| 50.0000 | 李四 | 2 |
+---------+--------+---------+
2 rows in set (0.00 sec)

mysql> #降序排 order by 列名 desc 降序/asc升序
mysql> select avg(score) as average ,name, sum(score<60) as subject from result group by name having subject>=2 order by add_time asc;
ERROR 1054 (42S22): Unknown column 'add_time' in 'order clause'
mysql> desc goods;
+--------------+------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------------+------+-----+---------+----------------+
| goods_id | mediumint(8) unsigned | NO | PRI | NULL | auto_increment |
| goods_name | varchar(120) | NO | | | |
| cat_id | smallint(5) unsigned | NO | | 0 | |
| brand_id | smallint(5) unsigned | NO | | 0 | |
| goods_sn | char(15) | NO | | | |
| goods_number | smallint(5) unsigned | NO | | 0 | |
| shop_price | decimal(10,2) unsigned | NO | | 0.00 | |
| market_price | decimal(10,2) unsigned | NO | | 0.00 | |
| click_count | int(10) unsigned | NO | | 0 | |
+--------------+------------------------+------+-----+---------+----------------+
9 rows in set (0.20 sec)

mysql> select goods_name ,cat_id,goods_id,shop_price from goods order by asc cat_id ,shop_price desc;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'asc cat_id ,shop_price desc' at line 1
mysql> select goods_name ,cat_id,goods_id,shop_price from goods order by cat_id asc ,shop_price desc;
+----------------------------------------+--------+----------+------------+
| goods_name | cat_id | goods_id | shop_price |
+----------------------------------------+--------+----------+------------+
| 恒基伟业g101 | 2 | 16 | 823.33 |
| 多普达touch hd | 3 | 22 | 5999.00 |
| 诺基亚n85 | 3 | 32 | 3010.00 |
| 夏新n7 | 3 | 17 | 2300.00 |
| 诺基亚e66 | 3 | 9 | 2298.00 |
| 金立 a30 | 3 | 21 | 2000.00 |
| p806 | 3 | 24 | 2000.00 |
| 摩托罗拉e8 | 3 | 31 | 1337.00 |
| 索爱c702c | 3 | 10 | 1328.00 |
| 诺基亚5320 xpressmusic | 3 | 13 | 1311.00 |
| 索爱c702c | 3 | 11 | 1300.00 |
| 摩托罗拉a810 | 3 | 12 | 983.00 |
| 三星sgh-f258 | 3 | 19 | 858.00 |
| 摩托罗拉a810 | 3 | 15 | 788.00 |
| 飞利浦9@9v | 3 | 8 | 399.00 |
| 三星bc01 | 3 | 20 | 280.00 |
| 夏新t5 | 4 | 18 | 2878.00 |
| 诺基亚5800xm | 4 | 14 | 2625.00 |
| kd876 | 4 | 1 | 1388.00 |
| 诺基亚n96 | 5 | 23 | 3700.00 |
| 诺基亚n85原装立体声耳机hs-82 | 8 | 7 | 100.00 |
| 诺基亚原装5800耳机 | 8 | 3 | 68.00 |
| 诺基亚n85原装充电器 | 8 | 4 | 58.00 |
| 胜创kingmax内存卡 | 11 | 6 | 42.00 |
| 索爱原装m2卡读卡器 | 11 | 5 | 20.00 |
| 小灵通/固话50元充值卡 | 13 | 25 | 48.00 |
| 小灵通/固话20元充值卡 | 13 | 26 | 19.00 |
| 移动100元充值卡 | 14 | 29 | 90.00 |
| 移动20元充值卡 | 14 | 30 | 18.00 |
| 联通100元充值卡 | 15 | 27 | 95.00 |
| 联通50元充值卡 | 15 | 28 | 45.00 |
+----------------------------------------+--------+----------+------------+
31 rows in set (0.26 sec)

mysql> #多排 用,隔开 order by cat_id asc ,shop_price desc
mysql> exit
mysql> use test01;
Database changed
mysql> #limit 限制条目
mysql> select goods_id,cat_id,goods_name,shop_price from goods where cat_id=3 order by shop_price desc limit 0,3;
+----------+--------+-------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+-------------------+------------+
| 22 | 3 | 多普达touch hd | 5999.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
+----------+--------+-------------------+------------+
3 rows in set (0.01 sec)

mysql> select goods_id,cat_id,goods_name,shop_price from goods where cat_id=3 order by shop_price desc limit 2,2;
+----------+--------+--------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------+------------+
| 17 | 3 | 夏新n7 | 2300.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
+----------+--------+--------------+------------+
2 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name,shop_price from goods where cat_id=3 order by shop_price desc limit 2,3;
+----------+--------+--------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------+------------+
| 17 | 3 | 夏新n7 | 2300.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
+----------+--------+--------------+------------+
3 rows in set (0.00 sec)

mysql> #limit 第一个参数为0可以不写
mysql> #查询出每个栏目下id号最大的一条商品
mysql> select goods_id,cat_id,goods_name,shop_price from goods where 1 group by cat_id order by goods_id desc limit 1;
+----------+--------+-----------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+-----------------------+------------+
| 29 | 14 | 移动100元充值卡 | 90.00 |
+----------+--------+-----------------------+------------+
1 row in set (0.06 sec)

mysql> select goods_id,cat_id,goods_name,shop_price from goods where 1 group by cat_id ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name,shop_price from goods group by cat_id ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select cat_id,goods_name,shop_price from goods group by cat_id ;
+--------+--------------------------------+------------+
| cat_id | goods_name | shop_price |
+--------+--------------------------------+------------+
| 4 | kd876 | 1388.00 |
| 8 | 诺基亚n85原装充电器 | 58.00 |
| 11 | 索爱原装m2卡读卡器 | 20.00 |
| 3 | 飞利浦9@9v | 399.00 |
| 2 | 恒基伟业g101 | 823.33 |
| 5 | 诺基亚n96 | 3700.00 |
| 13 | 小灵通/固话50元充值卡 | 48.00 |
| 15 | 联通100元充值卡 | 95.00 |
| 14 | 移动100元充值卡 | 90.00 |
+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods group by cat_id=3 ;
+----------+--------+---------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+---------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
+----------+--------+---------------+------------+
2 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 24 | 3 | p806 | 2000.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods group by cat_id ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 24 | 3 | p806 | 2000.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 1 | 4 | kd876 | 1388.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc ;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 24 | 3 | p806 | 2000.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 1 | 4 | kd876 | 1388.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods group by cat_id order by cat_id asc ,goods_id desc ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 1 | 4 | kd876 | 1388.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc ;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 24 | 3 | p806 | 2000.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 1 | 4 | kd876 | 1388.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select * from (select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc) as tem group by cat_id ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.04 sec)

mysql> select * from (select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc) as tem group by cat_id order by cat_id asc ,goods_id desc limit 1 ;
+----------+--------+------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
+----------+--------+------------------+------------+
1 row in set (0.00 sec)

mysql> select * from (select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc) as tem group by cat_id order by cat_id asc ,goods_id desc ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 1 | 4 | kd876 | 1388.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc ;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 24 | 3 | p806 | 2000.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 1 | 4 | kd876 | 1388.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select * from (select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc) as temp order by cat_id asc ;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 24 | 3 | p806 | 2000.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 1 | 4 | kd876 | 1388.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select * from (select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc) as temp group by cat_id order by cat_id asc ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 1 | 4 | kd876 | 1388.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select * from (select goods_id, cat_id,goods_name,shop_price from goods order by cat_id asc ,goods_id desc) as temp group by cat_id ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)


mysql> select goods_id, cat_id,goods_name,shop_price from goods where cat_id=3 order by goods_id desc limit 1 ;
+----------+--------+--------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------+------------+
| 32 | 3 | 诺基亚n85 | 3010.00 |
+----------+--------+--------------+------------+
1 row in set (0.07 sec)


mysql> select goods_id, cat_id,goods_name,shop_price from goods order by goods_id desc limit 1 ;
+----------+--------+--------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------+------------+
| 32 | 3 | 诺基亚n85 | 3010.00 |
+----------+--------+--------------+------------+
1 row in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods order by goods_id desc limit 1 ;
+----------+--------+--------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------+------------+
| 32 | 3 | 诺基亚n85 | 3010.00 |
+----------+--------+--------------+------------+
1 row in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods order by goods_id desc ;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 24 | 3 | p806 | 2000.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 1 | 4 | kd876 | 1388.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods group by cat_id order by goods_id desc ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 1 | 4 | kd876 | 1388.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods group by cat_id ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods group by cat_id order by goods_id desc ;
+----------+--------+--------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------------------------+------------+
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 1 | 4 | kd876 | 1388.00 |
+----------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id,goods_name,shop_price from goods order by goods_id desc limit 1 ;
+----------+--------+--------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+--------------+------------+
| 32 | 3 | 诺基亚n85 | 3010.00 |
+----------+--------+--------------+------------+
1 row in set (0.00 sec)

mysql> select max(goods_id), cat_id,goods_name,shop_price from goods order by goods_id desc ;
+---------------+--------+------------+------------+
| max(goods_id) | cat_id | goods_name | shop_price |
+---------------+--------+------------+------------+
| 32 | 4 | kd876 | 1388.00 |
+---------------+--------+------------+------------+
1 row in set (0.06 sec)

mysql> select goods_id ,cat_id ,goods_name from goods
-> ;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 3 | 8 | 诺基亚原装5800耳机 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 6 | 11 | 胜创kingmax内存卡 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 8 | 3 | 飞利浦9@9v |
| 9 | 3 | 诺基亚e66 |
| 10 | 3 | 索爱c702c |
| 11 | 3 | 索爱c702c |
| 12 | 3 | 摩托罗拉a810 |
| 13 | 3 | 诺基亚5320 xpressmusic |
| 14 | 4 | 诺基亚5800xm |
| 15 | 3 | 摩托罗拉a810 |
| 16 | 2 | 恒基伟业g101 |
| 17 | 3 | 夏新n7 |
| 18 | 4 | 夏新t5 |
| 19 | 3 | 三星sgh-f258 |
| 20 | 3 | 三星bc01 |
| 21 | 3 | 金立 a30 |
| 22 | 3 | 多普达touch hd |
| 23 | 5 | 诺基亚n96 |
| 24 | 3 | p806 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 28 | 15 | 联通50元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 31 | 3 | 摩托罗拉e8 |
| 32 | 3 | 诺基亚n85 |
+----------+--------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select max(goods_id), cat_id,goods_name,shop_price from goods group by cat_id ;
+---------------+--------+--------------------------------+------------+
| max(goods_id) | cat_id | goods_name | shop_price |
+---------------+--------+--------------------------------+------------+
| 18 | 4 | kd876 | 1388.00 |
| 7 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 6 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 32 | 3 | 飞利浦9@9v | 399.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 26 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 28 | 15 | 联通100元充值卡 | 95.00 |
| 30 | 14 | 移动100元充值卡 | 90.00 |
+---------------+--------+--------------------------------+------------+
9 rows in set (0.00 sec)

mysql> select max(goods_id), cat_id from goods group by cat_id ;
+---------------+--------+
| max(goods_id) | cat_id |
+---------------+--------+
| 18 | 4 |
| 7 | 8 |
| 6 | 11 |
| 32 | 3 |
| 16 | 2 |
| 23 | 5 |
| 26 | 13 |
| 28 | 15 |
| 30 | 14 |
+---------------+--------+
9 rows in set (0.00 sec)

mysql> select * from (select max(goods_id) as goods_id, cat_id from goods group by cat_id ) as temp where cat_id=cat_id ;
+----------+--------+
| goods_id | cat_id |
+----------+--------+
| 18 | 4 |
| 7 | 8 |
| 6 | 11 |
| 32 | 3 |
| 16 | 2 |
| 23 | 5 |
| 26 | 13 |
| 28 | 15 |
| 30 | 14 |
+----------+--------+
9 rows in set (0.06 sec)

mysql> select cat_id ,count(goods_name) from goods group by cat_id;
+--------+-------------------+
| cat_id | count(goods_name) |
+--------+-------------------+
| 4 | 3 |
| 8 | 3 |
| 11 | 2 |
| 3 | 15 |
| 2 | 1 |
| 5 | 1 |
| 13 | 2 |
| 15 | 2 |
| 14 | 2 |
+--------+-------------------+
9 rows in set (0.00 sec)

mysql> select cat_id ,max(goods_id) from goods group by cat_id;
+--------+---------------+
| cat_id | max(goods_id) |
+--------+---------------+
| 4 | 18 |
| 8 | 7 |
| 11 | 6 |
| 3 | 32 |
| 2 | 16 |
| 5 | 23 |
| 13 | 26 |
| 15 | 28 |
| 14 | 30 |
+--------+---------------+
9 rows in set (0.00 sec)


mysql> select cat_id ,max(goods_id),max(goods_name) from goods group by cat_id;
+--------+---------------+--------------------------------+
| cat_id | max(goods_id) | max(goods_name) |
+--------+---------------+--------------------------------+
| 4 | 18 | 诺基亚5800xm |
| 8 | 7 | 诺基亚原装5800耳机 |
| 11 | 6 | 胜创kingmax内存卡 |
| 3 | 32 | 飞利浦9@9v |
| 2 | 16 | 恒基伟业g101 |
| 5 | 23 | 诺基亚n96 |
| 13 | 26 | 小灵通/固话50元充值卡 |
| 15 | 28 | 联通50元充值卡 |
| 14 | 30 | 移动20元充值卡 |
+--------+---------------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select cat_id ,max(goods_id) from goods ;
+--------+---------------+
| cat_id | max(goods_id) |
+--------+---------------+
| 4 | 32 |
+--------+---------------+
1 row in set (0.00 sec)

mysql> select cat_id, goods_id,goods_name from goods order by goods_id desc ;
+--------+----------+----------------------------------------+
| cat_id | goods_id | goods_name |
+--------+----------+----------------------------------------+
| 3 | 32 | 诺基亚n85 |
| 3 | 31 | 摩托罗拉e8 |
| 14 | 30 | 移动20元充值卡 |
| 14 | 29 | 移动100元充值卡 |
| 15 | 28 | 联通50元充值卡 |
| 15 | 27 | 联通100元充值卡 |
| 13 | 26 | 小灵通/固话20元充值卡 |
| 13 | 25 | 小灵通/固话50元充值卡 |
| 3 | 24 | p806 |
| 5 | 23 | 诺基亚n96 |
| 3 | 22 | 多普达touch hd |
| 3 | 21 | 金立 a30 |
| 3 | 20 | 三星bc01 |
| 3 | 19 | 三星sgh-f258 |
| 4 | 18 | 夏新t5 |
| 3 | 17 | 夏新n7 |
| 2 | 16 | 恒基伟业g101 |
| 3 | 15 | 摩托罗拉a810 |
| 4 | 14 | 诺基亚5800xm |
| 3 | 13 | 诺基亚5320 xpressmusic |
| 3 | 12 | 摩托罗拉a810 |
| 3 | 11 | 索爱c702c |
| 3 | 10 | 索爱c702c |
| 3 | 9 | 诺基亚e66 |
| 3 | 8 | 飞利浦9@9v |
| 8 | 7 | 诺基亚n85原装立体声耳机hs-82 |
| 11 | 6 | 胜创kingmax内存卡 |
| 11 | 5 | 索爱原装m2卡读卡器 |
| 8 | 4 | 诺基亚n85原装充电器 |
| 8 | 3 | 诺基亚原装5800耳机 |
| 4 | 1 | kd876 |
+--------+----------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select cat_id ,max(goods_id) from goods ;
+--------+---------------+
| cat_id | max(goods_id) |
+--------+---------------+
| 4 | 32 |
+--------+---------------+
1 row in set (0.00 sec)

mysql> select cat_id, goods_id,goods_name from goods order by goods_id desc ;
+--------+----------+----------------------------------------+
| cat_id | goods_id | goods_name |
+--------+----------+----------------------------------------+
| 3 | 32 | 诺基亚n85 |
| 3 | 31 | 摩托罗拉e8 |
| 14 | 30 | 移动20元充值卡 |
| 14 | 29 | 移动100元充值卡 |
| 15 | 28 | 联通50元充值卡 |
| 15 | 27 | 联通100元充值卡 |
| 13 | 26 | 小灵通/固话20元充值卡 |
| 13 | 25 | 小灵通/固话50元充值卡 |
| 3 | 24 | p806 |
| 5 | 23 | 诺基亚n96 |
| 3 | 22 | 多普达touch hd |
| 3 | 21 | 金立 a30 |
| 3 | 20 | 三星bc01 |
| 3 | 19 | 三星sgh-f258 |
| 4 | 18 | 夏新t5 |
| 3 | 17 | 夏新n7 |
| 2 | 16 | 恒基伟业g101 |
| 3 | 15 | 摩托罗拉a810 |
| 4 | 14 | 诺基亚5800xm |
| 3 | 13 | 诺基亚5320 xpressmusic |
| 3 | 12 | 摩托罗拉a810 |
| 3 | 11 | 索爱c702c |
| 3 | 10 | 索爱c702c |
| 3 | 9 | 诺基亚e66 |
| 3 | 8 | 飞利浦9@9v |
| 8 | 7 | 诺基亚n85原装立体声耳机hs-82 |
| 11 | 6 | 胜创kingmax内存卡 |
| 11 | 5 | 索爱原装m2卡读卡器 |
| 8 | 4 | 诺基亚n85原装充电器 |
| 8 | 3 | 诺基亚原装5800耳机 |
| 4 | 1 | kd876 |
+--------+----------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select cat_id ,max(goods_id) from goods ;
+--------+---------------+
| cat_id | max(goods_id) |
+--------+---------------+
| 4 | 32 |
+--------+---------------+
1 row in set (0.00 sec)

mysql> select cat_id ,max(goods_id) from goods group by cat_id;
+--------+---------------+
| cat_id | max(goods_id) |
+--------+---------------+
| 4 | 18 |
| 8 | 7 |
| 11 | 6 |
| 3 | 32 |
| 2 | 16 |
| 5 | 23 |
| 13 | 26 |
| 15 | 28 |
| 14 | 30 |
+--------+---------------+
9 rows in set (0.00 sec)


mysql> select goods_id ,goods_name,cat_id from goods where goods_id in(select max(goods_id) from goods group by cat_id) ;
+----------+----------------------------------------+--------+
| goods_id | goods_name | cat_id |
+----------+----------------------------------------+--------+
| 6 | 胜创kingmax内存卡 | 11 |
| 7 | 诺基亚n85原装立体声耳机hs-82 | 8 |
| 16 | 恒基伟业g101 | 2 |
| 18 | 夏新t5 | 4 |
| 23 | 诺基亚n96 | 5 |
| 26 | 小灵通/固话20元充值卡 | 13 |
| 28 | 联通50元充值卡 | 15 |
| 30 | 移动20元充值卡 | 14 |
| 32 | 诺基亚n85 | 3 |
+----------+----------------------------------------+--------+
9 rows in set (0.06 sec)

mysql> select * from(select goods_id,cat_id ,goods_name from goods order by goods_id desc ) as temp group by cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)


mysql> select * from(select goods_id,cat_id ,goods_name from goods order by goods_id desc) as temp group by temp.cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select goods_id,cat_id ,goods_name from goods order by goods_id desc;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 32 | 3 | 诺基亚n85 |
| 31 | 3 | 摩托罗拉e8 |
| 30 | 14 | 移动20元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 28 | 15 | 联通50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 24 | 3 | p806 |
| 23 | 5 | 诺基亚n96 |
| 22 | 3 | 多普达touch hd |
| 21 | 3 | 金立 a30 |
| 20 | 3 | 三星bc01 |
| 19 | 3 | 三星sgh-f258 |
| 18 | 4 | 夏新t5 |
| 17 | 3 | 夏新n7 |
| 16 | 2 | 恒基伟业g101 |
| 15 | 3 | 摩托罗拉a810 |
| 14 | 4 | 诺基亚5800xm |
| 13 | 3 | 诺基亚5320 xpressmusic |
| 12 | 3 | 摩托罗拉a810 |
| 11 | 3 | 索爱c702c |
| 10 | 3 | 索爱c702c |
| 9 | 3 | 诺基亚e66 |
| 8 | 3 | 飞利浦9@9v |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 6 | 11 | 胜创kingmax内存卡 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 3 | 8 | 诺基亚原装5800耳机 |
| 1 | 4 | kd876 |
+----------+--------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select cat_id,goods_name from (select goods_id,cat_id ,goods_name from goods order by goods_id desc) as temp group by cat_id;
+--------+--------------------------------+
| cat_id | goods_name |
+--------+--------------------------------+
| 4 | kd876 |
| 8 | 诺基亚n85原装充电器 |
| 11 | 索爱原装m2卡读卡器 |
| 3 | 飞利浦9@9v |
| 2 | 恒基伟业g101 |
| 5 | 诺基亚n96 |
| 13 | 小灵通/固话50元充值卡 |
| 15 | 联通100元充值卡 |
| 14 | 移动100元充值卡 |
+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select temp.cat_id,goods_name from (select goods_id,cat_id ,goods_name from goods order by goods_id desc) as temp group by temp.cat_id;
+--------+--------------------------------+
| cat_id | goods_name |
+--------+--------------------------------+
| 4 | kd876 |
| 8 | 诺基亚n85原装充电器 |
| 11 | 索爱原装m2卡读卡器 |
| 3 | 飞利浦9@9v |
| 2 | 恒基伟业g101 |
| 5 | 诺基亚n96 |
| 13 | 小灵通/固话50元充值卡 |
| 15 | 联通100元充值卡 |
| 14 | 移动100元充值卡 |
+--------+--------------------------------+
9 rows in set (0.05 sec)

mysql> #子查询
mysql> #查询商品id最大的商品不用排序
mysql> select goods_id ,cat_id ,goods_name from goods where goods_id=(select max(goods_id) from goods);
+----------+--------+--------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------+
| 32 | 3 | 诺基亚n85 |
+----------+--------+--------------+
1 row in set (0.05 sec)

mysql> #如果where型子查询 即where 列=(内层sql 返回的是必是单行单列单个值,) 若where 列 in(内层sql)只能是单列多行
mysql> #from型子查询,内部查询的结果当作外部查询的表s
mysql> select goods_id ,cat_id ,goods_name from (select goods_id ,cat_id ,goods_name from goods order by cat_id asc,goods_id desc) as temp group by cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select goods_id ,cat_id ,goods_name from goods order by cat_id asc,goods_id desc;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 16 | 2 | 恒基伟业g101 |
| 32 | 3 | 诺基亚n85 |
| 31 | 3 | 摩托罗拉e8 |
| 24 | 3 | p806 |
| 22 | 3 | 多普达touch hd |
| 21 | 3 | 金立 a30 |
| 20 | 3 | 三星bc01 |
| 19 | 3 | 三星sgh-f258 |
| 17 | 3 | 夏新n7 |
| 15 | 3 | 摩托罗拉a810 |
| 13 | 3 | 诺基亚5320 xpressmusic |
| 12 | 3 | 摩托罗拉a810 |
| 11 | 3 | 索爱c702c |
| 10 | 3 | 索爱c702c |
| 9 | 3 | 诺基亚e66 |
| 8 | 3 | 飞利浦9@9v |
| 18 | 4 | 夏新t5 |
| 14 | 4 | 诺基亚5800xm |
| 1 | 4 | kd876 |
| 23 | 5 | 诺基亚n96 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 3 | 8 | 诺基亚原装5800耳机 |
| 6 | 11 | 胜创kingmax内存卡 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 28 | 15 | 联通50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
+----------+--------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select * from (select goods_id ,cat_id ,goods_name from goods order by cat_id asc,goods_id desc) as temp group by cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select * from (select goods_id ,cat_id ,goods_name from goods order by cat_id asc,goods_id desc) as temp group by temp.cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name from (select goods_id as goods_id ,cat_id as cat_id ,goods_name as goods_name from goods order by cat_id asc,goods_id desc) as temp group by temp.cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select goods_id, cat_id, goods_name from (select goods_id, goods_name, cat_id from goods order by cat_id asc, goods_id desc) as tmp group by cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> exit
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| bookstore |
| clouddb01 |
| clouddb02 |
| clouddb03 |
| information_schema |
| mydb |
| mysql |
| performance_schema |
| shop |
| ssm_crud |
| struts |
| student |
| sys |
| test |
| test01 |
+--------------------+
15 rows in set (0.35 sec)

mysql> use test01;
Database changed
mysql> select goods_id,cat_id,goods_name from goods order by goods_id desc ,cat_id asc;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 32 | 3 | 诺基亚n85 |
| 31 | 3 | 摩托罗拉e8 |
| 30 | 14 | 移动20元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 28 | 15 | 联通50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 24 | 3 | p806 |
| 23 | 5 | 诺基亚n96 |
| 22 | 3 | 多普达touch hd |
| 21 | 3 | 金立 a30 |
| 20 | 3 | 三星bc01 |
| 19 | 3 | 三星sgh-f258 |
| 18 | 4 | 夏新t5 |
| 17 | 3 | 夏新n7 |
| 16 | 2 | 恒基伟业g101 |
| 15 | 3 | 摩托罗拉a810 |
| 14 | 4 | 诺基亚5800xm |
| 13 | 3 | 诺基亚5320 xpressmusic |
| 12 | 3 | 摩托罗拉a810 |
| 11 | 3 | 索爱c702c |
| 10 | 3 | 索爱c702c |
| 9 | 3 | 诺基亚e66 |
| 8 | 3 | 飞利浦9@9v |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 6 | 11 | 胜创kingmax内存卡 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 3 | 8 | 诺基亚原装5800耳机 |
| 1 | 4 | kd876 |
+----------+--------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name from goods order by cat_id desc ;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 27 | 15 | 联通100元充值卡 |
| 28 | 15 | 联通50元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 6 | 11 | 胜创kingmax内存卡 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 3 | 8 | 诺基亚原装5800耳机 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 23 | 5 | 诺基亚n96 |
| 1 | 4 | kd876 |
| 14 | 4 | 诺基亚5800xm |
| 18 | 4 | 夏新t5 |
| 8 | 3 | 飞利浦9@9v |
| 9 | 3 | 诺基亚e66 |
| 10 | 3 | 索爱c702c |
| 11 | 3 | 索爱c702c |
| 12 | 3 | 摩托罗拉a810 |
| 13 | 3 | 诺基亚5320 xpressmusic |
| 15 | 3 | 摩托罗拉a810 |
| 17 | 3 | 夏新n7 |
| 19 | 3 | 三星sgh-f258 |
| 20 | 3 | 三星bc01 |
| 21 | 3 | 金立 a30 |
| 22 | 3 | 多普达touch hd |
| 24 | 3 | p806 |
| 31 | 3 | 摩托罗拉e8 |
| 32 | 3 | 诺基亚n85 |
| 16 | 2 | 恒基伟业g101 |
+----------+--------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name from(select goods_id,cat_id,goods_name from goods order by cat_id,goods_id desc) as tmp;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 16 | 2 | 恒基伟业g101 |
| 32 | 3 | 诺基亚n85 |
| 31 | 3 | 摩托罗拉e8 |
| 24 | 3 | p806 |
| 22 | 3 | 多普达touch hd |
| 21 | 3 | 金立 a30 |
| 20 | 3 | 三星bc01 |
| 19 | 3 | 三星sgh-f258 |
| 17 | 3 | 夏新n7 |
| 15 | 3 | 摩托罗拉a810 |
| 13 | 3 | 诺基亚5320 xpressmusic |
| 12 | 3 | 摩托罗拉a810 |
| 11 | 3 | 索爱c702c |
| 10 | 3 | 索爱c702c |
| 9 | 3 | 诺基亚e66 |
| 8 | 3 | 飞利浦9@9v |
| 18 | 4 | 夏新t5 |
| 14 | 4 | 诺基亚5800xm |
| 1 | 4 | kd876 |
| 23 | 5 | 诺基亚n96 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 3 | 8 | 诺基亚原装5800耳机 |
| 6 | 11 | 胜创kingmax内存卡 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 28 | 15 | 联通50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
+----------+--------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name from(select goods_id,cat_id,goods_name from goods order by cat_id,goods_id desc) as tmp group by cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 1 | 4 | kd876 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 8 | 3 | 飞利浦9@9v |
| 16 | 2 | 恒基伟业g101 |
| 23 | 5 | 诺基亚n96 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
| 29 | 14 | 移动100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)


mysql> desc goods;
+--------------+------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------------+------+-----+---------+----------------+
| goods_id | mediumint(8) unsigned | NO | PRI | NULL | auto_increment |
| goods_name | varchar(120) | NO | | | |
| cat_id | smallint(5) unsigned | NO | | 0 | |
| brand_id | smallint(5) unsigned | NO | | 0 | |
| goods_sn | char(15) | NO | | | |
| goods_number | smallint(5) unsigned | NO | | 0 | |
| shop_price | decimal(10,2) unsigned | NO | | 0.00 | |
| market_price | decimal(10,2) unsigned | NO | | 0.00 | |
| click_count | int(10) unsigned | NO | | 0 | |
+--------------+------------------------+------+-----+---------+----------------+
9 rows in set (0.18 sec)


mysql> alter table goods add index cat(cat_id);
Query OK, 31 rows affected (1.05 sec)
Records: 31 Duplicates: 0 Warnings: 0

mysql> select goods_id,cat_id,goods_name from(select goods_id,cat_id,goods_name from goods order by cat_id,goods_id desc) as tmp group by cat_id;
+----------+--------+--------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+--------------------------------+
| 16 | 2 | 恒基伟业g101 |
| 8 | 3 | 飞利浦9@9v |
| 1 | 4 | kd876 |
| 23 | 5 | 诺基亚n96 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 27 | 15 | 联通100元充值卡 |
+----------+--------+--------------------------------+
9 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name from(select goods_id,cat_id,goods_name from goods order by cat_id,goods_id desc limit 1000) as tmp group by cat_id;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 16 | 2 | 恒基伟业g101 |
| 32 | 3 | 诺基亚n85 |
| 18 | 4 | 夏新t5 |
| 23 | 5 | 诺基亚n96 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 6 | 11 | 胜创kingmax内存卡 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 28 | 15 | 联通50元充值卡 |
+----------+--------+----------------------------------------+
9 rows in set (0.00 sec)


mysql> select goods_id,cat_id,goods_name from goods where goods_id in(select max(goods_id) from goods group by cat_id) group by cat_id;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 16 | 2 | 恒基伟业g101 |
| 32 | 3 | 诺基亚n85 |
| 18 | 4 | 夏新t5 |
| 23 | 5 | 诺基亚n96 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 6 | 11 | 胜创kingmax内存卡 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 28 | 15 | 联通50元充值卡 |
+----------+--------+----------------------------------------+
9 rows in set (0.04 sec)

mysql> #exits子查询
mysql> #from子查询的排序要加limit\
mysql> #exists 存在,exists 子查询
mysql> #查出有商品的栏目
mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| girl |
| goods |
| m |
| mian |
| result |
| t |
| user |
+------------------+
11 rows in set (0.06 sec)

mysql> desc category;
+-----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+----------------------+------+-----+---------+----------------+
| cat_id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| cat_name | varchar(90) | NO | | | |
| parent_id | smallint(5) unsigned | YES | | NULL | |
+-----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

mysql> select * from category;
+--------+---------------------------+-----------+
| cat_id | cat_name | parent_id |
+--------+---------------------------+-----------+
| 1 | 手机类型 | 0 |
| 2 | CDMA手机 | 1 |
| 3 | GSM手机 | 1 |
| 4 | 3G手机 | 1 |
| 5 | 双模手机 | 1 |
| 6 | 手机配件 | 0 |
| 7 | 充电器 | 6 |
| 8 | 耳机 | 6 |
| 9 | 电池 | 6 |
| 11 | 读卡器和内存卡 | 6 |
| 12 | 充值卡 | 0 |
| 13 | 小灵通/固话充值卡 | 12 |
| 14 | 移动手机充值卡 | 12 |
| 15 | 联通手机充值卡 | 12 |
+--------+---------------------------+-----------+
14 rows in set (0.07 sec)

mysql> desc goods;
+--------------+------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------------+------+-----+---------+----------------+
| goods_id | mediumint(8) unsigned | NO | PRI | NULL | auto_increment |
| goods_name | varchar(120) | NO | | | |
| cat_id | smallint(5) unsigned | NO | MUL | 0 | |
| brand_id | smallint(5) unsigned | NO | | 0 | |
| goods_sn | char(15) | NO | | | |
| goods_number | smallint(5) unsigned | NO | | 0 | |
| shop_price | decimal(10,2) unsigned | NO | | 0.00 | |
| market_price | decimal(10,2) unsigned | NO | | 0.00 | |
| click_count | int(10) unsigned | NO | | 0 | |
+--------------+------------------------+------+-----+---------+----------------+
9 rows in set (0.00 sec)


mysql> show index from goods;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+
| goods | 0 | PRIMARY | 1 | goods_id | A | 31 | NULL | NULL | | BTREE | | | YES |
| goods | 1 | cat | 1 | cat_id | A | NULL | NULL | NULL | | BTREE | | | YES |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+
2 rows in set (0.17 sec)

mysql> drop index cat on goods;
Query OK, 31 rows affected (0.55 sec)
Records: 31 Duplicates: 0 Warnings: 0

mysql> show index from goods;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+
| goods | 0 | PRIMARY | 1 | goods_id | A | 31 | NULL | NULL | | BTREE | | | YES |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+
1 row in set (0.00 sec)

mysql> desc goods;
+--------------+------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------------+------+-----+---------+----------------+
| goods_id | mediumint(8) unsigned | NO | PRI | NULL | auto_increment |
| goods_name | varchar(120) | NO | | | |
| cat_id | smallint(5) unsigned | NO | | 0 | |
| brand_id | smallint(5) unsigned | NO | | 0 | |
| goods_sn | char(15) | NO | | | |
| goods_number | smallint(5) unsigned | NO | | 0 | |
| shop_price | decimal(10,2) unsigned | NO | | 0.00 | |
| market_price | decimal(10,2) unsigned | NO | | 0.00 | |
| click_count | int(10) unsigned | NO | | 0 | |
+--------------+------------------------+------+-----+---------+----------------+
9 rows in set (0.00 sec)

mysql> desc category;
+-----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+----------------------+------+-----+---------+----------------+
| cat_id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| cat_name | varchar(90) | NO | | | |
| parent_id | smallint(5) unsigned | YES | | NULL | |
+-----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.03 sec)

mysql> select cat_name from category;
+---------------------------+
| cat_name |
+---------------------------+
| 手机类型 |
| CDMA手机 |
| GSM手机 |
| 3G手机 |
| 双模手机 |
| 手机配件 |
| 充电器 |
| 耳机 |
| 电池 |
| 读卡器和内存卡 |
| 充值卡 |
| 小灵通/固话充值卡 |
| 移动手机充值卡 |
| 联通手机充值卡 |
+---------------------------+
14 rows in set (0.00 sec)

mysql> select cat_id,cat_name from category where exists(select * from goods where category.cat_id=goods_id);
+--------+---------------------------+
| cat_id | cat_name |
+--------+---------------------------+
| 1 | 手机类型 |
| 3 | GSM手机 |
| 4 | 3G手机 |
| 5 | 双模手机 |
| 6 | 手机配件 |
| 7 | 充电器 |
| 8 | 耳机 |
| 9 | 电池 |
| 11 | 读卡器和内存卡 |
| 12 | 充值卡 |
| 13 | 小灵通/固话充值卡 |
| 14 | 移动手机充值卡 |
| 15 | 联通手机充值卡 |
+--------+---------------------------+
13 rows in set (0.00 sec)

mysql> select cat_id,cat_name from category where exists(select * from goods where category.cat_id=goods.cat_id);
+--------+---------------------------+
| cat_id | cat_name |
+--------+---------------------------+
| 2 | CDMA手机 |
| 3 | GSM手机 |
| 4 | 3G手机 |
| 5 | 双模手机 |
| 8 | 耳机 |
| 11 | 读卡器和内存卡 |
| 13 | 小灵通/固话充值卡 |
| 14 | 移动手机充值卡 |
| 15 | 联通手机充值卡 |
+--------+---------------------------+
9 rows in set (0.00 sec)

mysql> #为什么建表时加not null或default 0 ,不想出现null值
mysql> #null判断只能用 is null 或is not nul
mysql> 
mysql> #效率不高,影响索引效率
mysql> select 100000*232344242
-> ;
+------------------+
| 100000*232344242 |
+------------------+
| 23234424200000 |
+------------------+
1 row in set (0.00 sec)

mysql> #左连接的语法
mysql> a表不动,b表在右边滑动
-> #
-> \n
ERROR: 
Unknown command '\n'.
-> ;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a表不动,b表在右边滑动

\n' at line 1
mysql> #a表与b表通过什么关联行
mysql> # a 表left join b on 条件 条件为真,则b表对应的行取出
mysql> # a left join b on
mysql> #将a left join b on 条件 设为c 表
mysql> #可以对c表进行查询,可以查询a和b的列
mysql> select goods_id,cat_id,cat_name from goods left join category on goods.cat_id=category.cat_id;
ERROR 1052 (23000): Column 'cat_id' in field list is ambiguous
mysql> select goods_id,goods.cat_id,cat_name from goods left join category on goods.cat_id=category.cat_id;
+----------+--------+---------------------------+
| goods_id | cat_id | cat_name |
+----------+--------+---------------------------+
| 1 | 4 | 3G手机 |
| 4 | 8 | 耳机 |
| 3 | 8 | 耳机 |
| 5 | 11 | 读卡器和内存卡 |
| 6 | 11 | 读卡器和内存卡 |
| 7 | 8 | 耳机 |
| 8 | 3 | GSM手机 |
| 9 | 3 | GSM手机 |
| 10 | 3 | GSM手机 |
| 11 | 3 | GSM手机 |
| 12 | 3 | GSM手机 |
| 13 | 3 | GSM手机 |
| 14 | 4 | 3G手机 |
| 15 | 3 | GSM手机 |
| 16 | 2 | CDMA手机 |
| 17 | 3 | GSM手机 |
| 18 | 4 | 3G手机 |
| 19 | 3 | GSM手机 |
| 20 | 3 | GSM手机 |
| 21 | 3 | GSM手机 |
| 22 | 3 | GSM手机 |
| 23 | 5 | 双模手机 |
| 24 | 3 | GSM手机 |
| 25 | 13 | 小灵通/固话充值卡 |
| 26 | 13 | 小灵通/固话充值卡 |
| 27 | 15 | 联通手机充值卡 |
| 28 | 15 | 联通手机充值卡 |
| 29 | 14 | 移动手机充值卡 |
| 30 | 14 | 移动手机充值卡 |
| 31 | 3 | GSM手机 |
| 32 | 3 | GSM手机 |
+----------+--------+---------------------------+
31 rows in set (0.00 sec)

mysql> select goods_id,goods.cat_id,cat_name,goods_name from goods left join category on goods.cat_id=category.cat_id;
+----------+--------+---------------------------+----------------------------------------+
| goods_id | cat_id | cat_name | goods_name |
+----------+--------+---------------------------+----------------------------------------+
| 1 | 4 | 3G手机 | kd876 |
| 4 | 8 | 耳机 | 诺基亚n85原装充电器 |
| 3 | 8 | 耳机 | 诺基亚原装5800耳机 |
| 5 | 11 | 读卡器和内存卡 | 索爱原装m2卡读卡器 |
| 6 | 11 | 读卡器和内存卡 | 胜创kingmax内存卡 |
| 7 | 8 | 耳机 | 诺基亚n85原装立体声耳机hs-82 |
| 8 | 3 | GSM手机 | 飞利浦9@9v |
| 9 | 3 | GSM手机 | 诺基亚e66 |
| 10 | 3 | GSM手机 | 索爱c702c |
| 11 | 3 | GSM手机 | 索爱c702c |
| 12 | 3 | GSM手机 | 摩托罗拉a810 |
| 13 | 3 | GSM手机 | 诺基亚5320 xpressmusic |
| 14 | 4 | 3G手机 | 诺基亚5800xm |
| 15 | 3 | GSM手机 | 摩托罗拉a810 |
| 16 | 2 | CDMA手机 | 恒基伟业g101 |
| 17 | 3 | GSM手机 | 夏新n7 |
| 18 | 4 | 3G手机 | 夏新t5 |
| 19 | 3 | GSM手机 | 三星sgh-f258 |
| 20 | 3 | GSM手机 | 三星bc01 |
| 21 | 3 | GSM手机 | 金立 a30 |
| 22 | 3 | GSM手机 | 多普达touch hd |
| 23 | 5 | 双模手机 | 诺基亚n96 |
| 24 | 3 | GSM手机 | p806 |
| 25 | 13 | 小灵通/固话充值卡 | 小灵通/固话50元充值卡 |
| 26 | 13 | 小灵通/固话充值卡 | 小灵通/固话20元充值卡 |
| 27 | 15 | 联通手机充值卡 | 联通100元充值卡 |
| 28 | 15 | 联通手机充值卡 | 联通50元充值卡 |
| 29 | 14 | 移动手机充值卡 | 移动100元充值卡 |
| 30 | 14 | 移动手机充值卡 | 移动20元充值卡 |
| 31 | 3 | GSM手机 | 摩托罗拉e8 |
| 32 | 3 | GSM手机 | 诺基亚n85 |
+----------+--------+---------------------------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> select goods_id,goods.cat_id,goods_name,cat_name from goods left join category on goods.cat_id=category.cat_id;
+----------+--------+----------------------------------------+---------------------------+
| goods_id | cat_id | goods_name | cat_name |
+----------+--------+----------------------------------------+---------------------------+
| 1 | 4 | kd876 | 3G手机 |
| 4 | 8 | 诺基亚n85原装充电器 | 耳机 |
| 3 | 8 | 诺基亚原装5800耳机 | 耳机 |
| 5 | 11 | 索爱原装m2卡读卡器 | 读卡器和内存卡 |
| 6 | 11 | 胜创kingmax内存卡 | 读卡器和内存卡 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 耳机 |
| 8 | 3 | 飞利浦9@9v | GSM手机 |
| 9 | 3 | 诺基亚e66 | GSM手机 |
| 10 | 3 | 索爱c702c | GSM手机 |
| 11 | 3 | 索爱c702c | GSM手机 |
| 12 | 3 | 摩托罗拉a810 | GSM手机 |
| 13 | 3 | 诺基亚5320 xpressmusic | GSM手机 |
| 14 | 4 | 诺基亚5800xm | 3G手机 |
| 15 | 3 | 摩托罗拉a810 | GSM手机 |
| 16 | 2 | 恒基伟业g101 | CDMA手机 |
| 17 | 3 | 夏新n7 | GSM手机 |
| 18 | 4 | 夏新t5 | 3G手机 |
| 19 | 3 | 三星sgh-f258 | GSM手机 |
| 20 | 3 | 三星bc01 | GSM手机 |
| 21 | 3 | 金立 a30 | GSM手机 |
| 22 | 3 | 多普达touch hd | GSM手机 |
| 23 | 5 | 诺基亚n96 | 双模手机 |
| 24 | 3 | p806 | GSM手机 |
| 25 | 13 | 小灵通/固话50元充值卡 | 小灵通/固话充值卡 |
| 26 | 13 | 小灵通/固话20元充值卡 | 小灵通/固话充值卡 |
| 27 | 15 | 联通100元充值卡 | 联通手机充值卡 |
| 28 | 15 | 联通50元充值卡 | 联通手机充值卡 |
| 29 | 14 | 移动100元充值卡 | 移动手机充值卡 |
| 30 | 14 | 移动20元充值卡 | 移动手机充值卡 |
| 31 | 3 | 摩托罗拉e8 | GSM手机 |
| 32 | 3 | 诺基亚n85 | GSM手机 |
+----------+--------+----------------------------------------+---------------------------+
31 rows in set (0.00 sec)

mysql> #取出第四个栏目的商品以及商品的栏目名称
mysql> select goods_id,goods.cat_id,goods_name,cat_name from goods left join category on goods.cat_id=category.cat_id where goods.cat_id=4;
+----------+--------+-----------------+----------+
| goods_id | cat_id | goods_name | cat_name |
+----------+--------+-----------------+----------+
| 1 | 4 | kd876 | 3G手机 |
| 14 | 4 | 诺基亚5800xm | 3G手机 |
| 18 | 4 | 夏新t5 | 3G手机 |
+----------+--------+-----------------+----------+
3 rows in set (0.07 sec)

mysql> #左右连接,左连接即左表不动,
mysql> #a left join b 并不是说 a 一定是在b的左边
mysql> #左右连接可以互换, a left join b =b right join a
mysql> # 内链接 特点 所有有配偶的男生/女生 走到舞台上来, 其 左表和右表不匹配的不能出现
mysql> # 集合的角度看,内链接是左右连接的交集;
mysql> # 外连接,求的是并集,但是在mysql中不支持
mysql> #左连接
mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| girl |
| goods |
| m |
| mian |
| result |
| t |
| user |
+------------------+
11 rows in set (0.60 sec)

mysql> select * from t;
+------+--------------+
| tid | tname |
+------+--------------+
| 1 | 国安 |
| 2 | 申花 |
| 3 | 布尔联队 |
+------+--------------+
3 rows in set (0.40 sec)

mysql> select * from m;
+------+------+------+------+------------+
| mid | hid | gid | mres | matime |
+------+------+------+------+------------+
| 1 | 1 | 2 | 2:0 | 2006-05-21 |
| 2 | 2 | 3 | 1:2 | 2006-06-21 |
| 3 | 3 | 1 | 2:5 | 2006-06-25 |
| 4 | 2 | 1 | 3:2 | 2006-07-21 |
+------+------+------+------+------------+
4 rows in set (0.10 sec)

mysql> select m.mid,m.hid,t.tname,m.gid,t.tname from m left join t on m.hid=t.tid;
+------+------+--------------+------+--------------+
| mid | hid | tname | gid | tname |
+------+------+--------------+------+--------------+
| 1 | 1 | 国安 | 2 | 国安 |
| 2 | 2 | 申花 | 3 | 申花 |
| 4 | 2 | 申花 | 1 | 申花 |
| 3 | 3 | 布尔联队 | 1 | 布尔联队 |
+------+------+--------------+------+--------------+
4 rows in set (0.00 sec)

mysql> select m.mid,m.hid,t.tname,m.gid from m left join t on m.hid=t.tid;
+------+------+--------------+------+
| mid | hid | tname | gid |
+------+------+--------------+------+
| 1 | 1 | 国安 | 2 |
| 2 | 2 | 申花 | 3 |
| 4 | 2 | 申花 | 1 |
| 3 | 3 | 布尔联队 | 1 |
+------+------+--------------+------+
4 rows in set (0.00 sec)


mysql> select tem.mid,tem.hid,t.tname,tem.gid,t.tname from (select m.mid,m.hid,t.tname,m.gid from m left join t on m.hid=t.tid) as tem left join t on t.tid=tem.gid;
+------+------+--------------+------+--------------+
| mid | hid | tname | gid | tname |
+------+------+--------------+------+--------------+
| 4 | 2 | 国安 | 1 | 国安 |
| 3 | 3 | 国安 | 1 | 国安 |
| 1 | 1 | 申花 | 2 | 申花 |
| 2 | 2 | 布尔联队 | 3 | 布尔联队 |
+------+------+--------------+------+--------------+
4 rows in set (0.00 sec)

mysql> select tem.mid,tem.hid,t.tname,tem.gid,t.tname from (select m.mid,m.hid,t.tname,m.gid from m left join t on m.hid=t.tid) as tem left join t on t.tid=tem.gid order by tem.mid asc;
+------+------+--------------+------+--------------+
| mid | hid | tname | gid | tname |
+------+------+--------------+------+--------------+
| 1 | 1 | 申花 | 2 | 申花 |
| 2 | 2 | 布尔联队 | 3 | 布尔联队 |
| 3 | 3 | 国安 | 1 | 国安 |
| 4 | 2 | 国安 | 1 | 国安 |
+------+------+--------------+------+--------------+
4 rows in set (0.00 sec)

mysql> select tem.mid,tem.hid,t.tname,tem.gid,t.tname from (select m.mid,m.hid,t.tname,m.gid from m left join t on m.hid=t.tid) as tem left join t on tem.gid=t.tid order by tem.mid asc;
+------+------+--------------+------+--------------+
| mid | hid | tname | gid | tname |
+------+------+--------------+------+--------------+
| 1 | 1 | 申花 | 2 | 申花 |
| 2 | 2 | 布尔联队 | 3 | 布尔联队 |
| 3 | 3 | 国安 | 1 | 国安 |
| 4 | 2 | 国安 | 1 | 国安 |
+------+------+--------------+------+--------------+
4 rows in set (0.00 sec)

mysql> select tem.mid,tem.hid,tem.tname,tem.gid,tem.tname from (select m.mid,m.hid,t.tname,m.gid from m left join t on m.hid=t.tid) as tem left join t on tem.gid=t.tid order by tem.mid asc;
+------+------+--------------+------+--------------+
| mid | hid | tname | gid | tname |
+------+------+--------------+------+--------------+
| 1 | 1 | 国安 | 2 | 国安 |
| 2 | 2 | 申花 | 3 | 申花 |
| 3 | 3 | 布尔联队 | 1 | 布尔联队 |
| 4 | 2 | 申花 | 1 | 申花 |
+------+------+--------------+------+--------------+
4 rows in set (0.00 sec)

mysql> select m.* from m left join t on m.hid=t.tid;
+------+------+------+------+------------+
| mid | hid | gid | mres | matime |
+------+------+------+------+------------+
| 1 | 1 | 2 | 2:0 | 2006-05-21 |
| 2 | 2 | 3 | 1:2 | 2006-06-21 |
| 4 | 2 | 1 | 3:2 | 2006-07-21 |
| 3 | 3 | 1 | 2:5 | 2006-06-25 |
+------+------+------+------+------------+
4 rows in set (0.00 sec)

mysql> select m.*,t.tname from m left join t on m.hid=t.tid;
+------+------+------+------+------------+--------------+
| mid | hid | gid | mres | matime | tname |
+------+------+------+------+------------+--------------+
| 1 | 1 | 2 | 2:0 | 2006-05-21 | 国安 |
| 2 | 2 | 3 | 1:2 | 2006-06-21 | 申花 |
| 4 | 2 | 1 | 3:2 | 2006-07-21 | 申花 |
| 3 | 3 | 1 | 2:5 | 2006-06-25 | 布尔联队 |
+------+------+------+------+------------+--------------+
4 rows in set (0.00 sec)


mysql> select tem.*, t.tname from (select m.*,t.tname from m left join t on m.hid=t.tid) as tem left join t on tem.gid=t.tid;
+------+------+------+------+------------+--------------+--------------+
| mid | hid | gid | mres | matime | tname | tname |
+------+------+------+------+------------+--------------+--------------+
| 4 | 2 | 1 | 3:2 | 2006-07-21 | 申花 | 国安 |
| 3 | 3 | 1 | 2:5 | 2006-06-25 | 布尔联队 | 国安 |
| 1 | 1 | 2 | 2:0 | 2006-05-21 | 国安 | 申花 |
| 2 | 2 | 3 | 1:2 | 2006-06-21 | 申花 | 布尔联队 |
+------+------+------+------+------------+--------------+--------------+
4 rows in set (0.00 sec)

mysql> select * from t;
+------+--------------+
| tid | tname |
+------+--------------+
| 1 | 国安 |
| 2 | 申花 |
| 3 | 布尔联队 |
+------+--------------+
3 rows in set (0.00 sec)

mysql> select tem.mid,tem.hid,tem.tname,tem.gid,t.tname,tem.mres,tem.matime from (select m.mid ,m.hid,t.tname,m.gid,m.mres,m.matime from m left join t on m.hid=t.tid) as tem left join t on tem.gid=t.tid;
+------+------+--------------+------+--------------+------+------------+
| mid | hid | tname | gid | tname | mres | matime |
+------+------+--------------+------+--------------+------+------------+
| 4 | 2 | 申花 | 1 | 国安 | 3:2 | 2006-07-21 |
| 3 | 3 | 布尔联队 | 1 | 国安 | 2:5 | 2006-06-25 |
| 1 | 1 | 国安 | 2 | 申花 | 2:0 | 2006-05-21 |
| 2 | 2 | 申花 | 3 | 布尔联队 | 1:2 | 2006-06-21 |
+------+------+--------------+------+--------------+------+------------+
4 rows in set (0.00 sec)

mysql> select tem.mid,tem.hid,tem.tname,tem.gid,t.tname,tem.mres,tem.matime from (select m.mid ,m.hid,t.tname,m.gid,m.mres,m.matime from m left join t on m.hid=t.tid) as tem left join t on tem.gid=t.tid order by tem.mid;
+------+------+--------------+------+--------------+------+------------+
| mid | hid | tname | gid | tname | mres | matime |
+------+------+--------------+------+--------------+------+------------+
| 1 | 1 | 国安 | 2 | 申花 | 2:0 | 2006-05-21 |
| 2 | 2 | 申花 | 3 | 布尔联队 | 1:2 | 2006-06-21 |
| 3 | 3 | 布尔联队 | 1 | 国安 | 2:5 | 2006-06-25 |
| 4 | 2 | 申花 | 1 | 国安 | 3:2 | 2006-07-21 |
+------+------+--------------+------+--------------+------+------------+
4 rows in set (0.00 sec)

mysql> select * from m;
+------+------+------+------+------------+
| mid | hid | gid | mres | matime |
+------+------+------+------+------------+
| 1 | 1 | 2 | 2:0 | 2006-05-21 |
| 2 | 2 | 3 | 1:2 | 2006-06-21 |
| 3 | 3 | 1 | 2:5 | 2006-06-25 |
| 4 | 2 | 1 | 3:2 | 2006-07-21 |
+------+------+------+------+------------+
4 rows in set (0.00 sec)

mysql> select tem.mid,tem.hid,tem.tname,tem.gid,t.tname,tem.mres,tem.matime from (select m.mid ,m.hid,t.tname,m.gid,m.mres,m.matime from m left join t on m.hid=t.tid) as tem left join t on tem.gid=t.tid where tem.matime between "2006-6-1" and "2006-7-1" order by tem.mid;
+------+------+--------------+------+--------------+------+------------+
| mid | hid | tname | gid | tname | mres | matime |
+------+------+--------------+------+--------------+------+------------+
| 2 | 2 | 申花 | 3 | 布尔联队 | 1:2 | 2006-06-21 |
| 3 | 3 | 布尔联队 | 1 | 国安 | 2:5 | 2006-06-25 |
+------+------+--------------+------+--------------+------+------------+
2 rows in set (0.06 sec)

mysql> select m.mid ,m.hid,t.tname,m.gid,tem.tname,m.mres,m.matime from m left join t on m.hid=t.tid left join t as tem on m.gid=tem.tid where m.matime between "2006-6-1" and "2006-7-1" order by m.mid;
+------+------+--------------+------+--------------+------+------------+
| mid | hid | tname | gid | tname | mres | matime |
+------+------+--------------+------+--------------+------+------------+
| 2 | 2 | 申花 | 3 | 布尔联队 | 1:2 | 2006-06-21 |
| 3 | 3 | 布尔联队 | 1 | 国安 | 2:5 | 2006-06-25 |
+------+------+--------------+------+--------------+------+------------+
2 rows in set (0.00 sec)

mysql> exit
mysql> use test01;
Database changed
mysql> select goods_id,goods_name,shop_price from goods where shop_price<50
-> ;
+----------+--------------------------------+------------+
| goods_id | goods_name | shop_price |
+----------+--------------------------------+------------+
| 5 | 索爱原装m2卡读卡器 | 20.00 |
| 6 | 胜创kingmax内存卡 | 42.00 |
| 25 | 小灵通/固话50元充值卡 | 48.00 |
| 26 | 小灵通/固话20元充值卡 | 19.00 |
| 28 | 联通50元充值卡 | 45.00 |
| 30 | 移动20元充值卡 | 18.00 |
+----------+--------------------------------+------------+
6 rows in set (0.14 sec)

mysql> #union 联合 语法 sql1 union sql2
mysql> select goods_id,goods_name,shop_price from goods where shop_price>4000;
+----------+-------------------+------------+
| goods_id | goods_name | shop_price |
+----------+-------------------+------------+
| 22 | 多普达touch hd | 5999.00 |
+----------+-------------------+------------+
1 row in set (0.00 sec)

mysql> select goods_id,goods_name,shop_price from goods where shop_price>4000 union select goods_id,goods_name,shop_price from goods where shop_price<50;
+----------+--------------------------------+------------+
| goods_id | goods_name | shop_price |
+----------+--------------------------------+------------+
| 22 | 多普达touch hd | 5999.00 |
| 5 | 索爱原装m2卡读卡器 | 20.00 |
| 6 | 胜创kingmax内存卡 | 42.00 |
| 25 | 小灵通/固话50元充值卡 | 48.00 |
| 26 | 小灵通/固话20元充值卡 | 19.00 |
| 28 | 联通50元充值卡 | 45.00 |
| 30 | 移动20元充值卡 | 18.00 |
+----------+--------------------------------+------------+
7 rows in set (0.10 sec)

mysql> #可以从两张表union联合查询
mysql> #两个列名不一致 以第一个列名为准
mysql> #union 满足的条件,只要结果集的列数一致就可以了
mysql> #union后的结果集可以排序
mysql> #格式: sql1 union sql2 order by
mysql> # 用nuion 取出第4个栏目和第5个栏目的商品m,并按价格升序排列
mysql> select goods_id ,cat_id, goods_name ,shop_price from goods union select goods_id ,cat_id ,goods_name ,shop_price from goods order by shop_price asc;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 1 | 4 | kd876 | 1388.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 24 | 3 | p806 | 2000.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 22 | 3 | 多普达touch hd | 5999.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.05 sec)

mysql> select goods_id ,cat_id, goods_name ,shop_price from goods where cat_id=4 union select goods_id ,cat_id ,goods_name ,shop_price from goods where cat_id=5 order by shop_price asc;
+----------+--------+-----------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+-----------------+------------+
| 1 | 4 | kd876 | 1388.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
+----------+--------+-----------------+------------+
4 rows in set (0.00 sec)

mysql> #取出第3个下价格前三高 的商品,和第四个栏目下价格前两高的商品用union完成

mysql> select goods_id ,cat_id,goods_name ,shop_price from goods where cat_id=3 order by shop_price desc limit 3;
+----------+--------+-------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+-------------------+------------+
| 22 | 3 | 多普达touch hd | 5999.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
+----------+--------+-------------------+------------+
3 rows in set (0.00 sec)

mysql> select goods_id ,cat_id ,goods_name ,shop_price from goods where cat_id=4 order by shop_price desc limit 2;
+----------+--------+-----------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+-----------------+------------+
| 18 | 4 | 夏新t5 | 2878.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
+----------+--------+-----------------+------------+
2 rows in set (0.00 sec)

mysql> (select goods_id ,cat_id,goods_name ,shop_price from goods where cat_id=3 order by shop_price desc limit 3) union (select goods_id ,cat_id,goods_name ,shop_price from goods where cat_id=4 order by shop_price desc limit 2);
+----------+--------+-------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+-------------------+------------+
| 22 | 3 | 多普达touch hd | 5999.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
+----------+--------+-------------------+------------+
5 rows in set (0.00 sec)

mysql> #这次内层的order by 不会失效是因为有limit,单纯的order by不会对结果集有影响,需要配合limit
mysql> #如果union后的结果有重复如何解决
mysql> #union会有去重的效果,不想去重可以用union all
mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| girl |
| goods |
| m |
| mian |
| result |
| t |
| user |
+------------------+
11 rows in set (0.08 sec)

mysql> select * from a;
+------+------+
| id | num |
+------+------+
| a | 5 |
| b | 10 |
| c | 15 |
| d | 10 |
+------+------+
4 rows in set (0.15 sec)

mysql> select * from b;
+------+------+
| id | num |
+------+------+
| b | 5 |
| c | 15 |
| d | 20 |
| e | 99 |
+------+------+
4 rows in set (0.02 sec)

mysql> select * from a union select * from b;
+------+------+
| id | num |
+------+------+
| a | 5 |
| b | 10 |
| c | 15 |
| d | 10 |
| b | 5 |
| d | 20 |
| e | 99 |
+------+------+
7 rows in set (0.00 sec)

mysql> select * from a union all select * from b;
+------+------+
| id | num |
+------+------+
| a | 5 |
| b | 10 |
| c | 15 |
| d | 10 |
| b | 5 |
| c | 15 |
| d | 20 |
| e | 99 |
+------+------+
8 rows in set (0.00 sec)

mysql> select * from a union all select * from b group by id;
+------+------+
| id | num |
+------+------+
| a | 5 |
| b | 10 |
| c | 15 |
| d | 10 |
| b | 5 |
| c | 15 |
| d | 20 |
| e | 99 |
+------+------+
8 rows in set (0.00 sec)

mysql> select tem.id,sum(tem.num) from(select a.id,a.num from a union all select b.id,b.num from b) as tem group by tem.id ;
+------+--------------+
| id | sum(tem.num) |
+------+--------------+
| a | 5 |
| b | 15 |
| c | 30 |
| d | 30 |
| e | 99 |
+------+--------------+
5 rows in set (0.00 sec)


mysql> select a.* ,b.* from a left join b on a.id=b.id;
+------+------+------+------+
| id | num | id | num |
+------+------+------+------+
| b | 10 | b | 5 |
| c | 15 | c | 15 |
| d | 10 | d | 20 |
| a | 5 | NULL | NULL |
+------+------+------+------+
4 rows in set (0.00 sec)

mysql> select a.* ,b.* from a inner join b on a.id=b.id;
+------+------+------+------+
| id | num | id | num |
+------+------+------+------+
| b | 10 | b | 5 |
| c | 15 | c | 15 |
| d | 10 | d | 20 |
+------+------+------+------+
3 rows in set (0.00 sec)

mysql> select a.* ,b.* from a left join b on a.id=b.id;
+------+------+------+------+
| id | num | id | num |
+------+------+------+------+
| b | 10 | b | 5 |
| c | 15 | c | 15 |
| d | 10 | d | 20 |
| a | 5 | NULL | NULL |
+------+------+------+------+
4 rows in set (0.00 sec)

mysql> select a.* ,b.* from a left join b on a.id=b.id union select a.* ,b.* from a right join b on a.id=b.id;
+------+------+------+------+
| id | num | id | num |
+------+------+------+------+
| b | 10 | b | 5 |
| c | 15 | c | 15 |
| d | 10 | d | 20 |
| a | 5 | NULL | NULL |
| NULL | NULL | e | 99 |
+------+------+------+------+
5 rows in set (0.00 sec)

mysql> #先左联再u右连然后子查询;
mysql> 
mysql> #函数
mysql> #取出第四个栏目的商品及打88折的会员价
mysql> select goods_id,cat_id,good_name,shop_price*0.88 from goods where cat_id=4 
-> ;
ERROR 1054 (42S22): Unknown column 'good_name' in 'field list'
mysql> select goods_id,cat_id,goods_name,shop_price*0.88 from goods where cat_id=4 
-> ;
+----------+--------+-----------------+-----------------+
| goods_id | cat_id | goods_name | shop_price*0.88 |
+----------+--------+-----------------+-----------------+
| 1 | 4 | kd876 | 1221.4400 |
| 14 | 4 | 诺基亚5800xm | 2310.0000 |
| 18 | 4 | 夏新t5 | 2532.6400 |
+----------+--------+-----------------+-----------------+
3 rows in set (0.00 sec)

mysql> select goods_id,cat_id,goods_name,floor(shop_price*0.88) from goods where cat_id=4 ;
+----------+--------+-----------------+------------------------+
| goods_id | cat_id | goods_name | floor(shop_price*0.88) |
+----------+--------+-----------------+------------------------+
| 1 | 4 | kd876 | 1221 |
| 14 | 4 | 诺基亚5800xm | 2310 |
| 18 | 4 | 夏新t5 | 2532 |
+----------+--------+-----------------+------------------------+
3 rows in set (0.00 sec)

mysql> #随机生成5-15之间的数字;


mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 7 |
+--------------------+
1 row in set (0.00 sec)

mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 13 |
+--------------------+
1 row in set (0.00 sec)

mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 8 |
+--------------------+
1 row in set (0.00 sec)

mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 9 |
+--------------------+
1 row in set (0.00 sec)

mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 8 |
+--------------------+
1 row in set (0.00 sec)

mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 5 |
+--------------------+
1 row in set (0.00 sec)

mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 8 |
+--------------------+
1 row in set (0.00 sec)

mysql> select floor(rand()*10+5);
+--------------------+
| floor(rand()*10+5) |
+--------------------+
| 11 |
+--------------------+
1 row in set (0.00 sec)

mysql> #ceiling 向上取整
mysql> #group concat 取出4栏目下goods_id拼接
mysql> select group_concat(goods_id) from goods where cat_id=4;
+------------------------+
| group_concat(goods_id) |
+------------------------+
| 1,14,18 |
+------------------------+
1 row in set (0.08 sec)

mysql> #计算字符的ascil码
mysql> select ascil(a);
ERROR 1305 (42000): FUNCTION test01.ascil does not exist
mysql> select ascii(a);
ERROR 1054 (42S22): Unknown column 'a' in 'field list'
mysql> select ascii('a');
+------------+
| ascii('a') |
+------------+
| 97 |
+------------+
1 row in set (0.00 sec)

mysql> select length("中华");
+------------------+
| length("中华") |
+------------------+
| 6 |
+------------------+
1 row in set (0.06 sec)

mysql> #length 计算的字节场地
mysql> #length 计算的字符数
mysql> #char_length 计算的字符数
mysql> select char_length('中国');
+-----------------------+
| char_length('中国') |
+-----------------------+
| 2 |
+-----------------------+
1 row in set (0.00 sec)

mysql> #反转字符串
mysql> select reverse('zh')
-> ;
+---------------+
| reverse('zh') |
+---------------+
| hz |
+---------------+
1 row in set (0.05 sec)

mysql> select reverse('zh中国');
+---------------------+
| reverse('zh中国') |
+---------------------+
| 国中hz |
+---------------------+
1 row in set (0.00 sec)

mysql> #position 
mysql> select position('@' in 'abc@sina.com');
+---------------------------------+
| position('@' in 'abc@sina.com') |
+---------------------------------+
| 4 |
+---------------------------------+
1 row in set (0.05 sec)

mysql> select right('abc@sina.com' ,2);
+--------------------------+
| right('abc@sina.com' ,2) |
+--------------------------+
| om |
+--------------------------+
1 row in set (0.00 sec)

mysql> #某网站有email字段,有邮件地址,想调查163.qq.com的u邮箱的比例
mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| girl |
| goods |
| m |
| mian |
| result |
| t |
| user |
+------------------+
11 rows in set (0.01 sec)

mysql> #查询邮箱后缀,
mysql> create table email(uname char,email char);
Query OK, 0 rows affected (1.76 sec)


mysql> desc email;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| uname | char(1) | YES | | NULL | |
| email | char(1) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.09 sec)


mysql> alter table email modify column uname char(50) ;
Query OK, 0 rows affected (1.96 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table email modify column email char(50) ;
Query OK, 0 rows affected (1.34 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> desc eamil;
ERROR 1146 (42S02): Table 'test01.eamil' doesn't exist
mysql> desc email;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| uname | char(50) | YES | | NULL | |
| email | char(50) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> insert into email values('zhangsan','zhan@163.com'),('lilie','li@qq.com'),('hanmeimei','han@126.com');
Query OK, 3 rows affected (0.28 sec)
Records: 3 Duplicates: 0 Warnings: 0

mysql> select * from email;
+-----------+--------------+
| uname | email |
+-----------+--------------+
| zhangsan | zhan@163.com |
| lilie | li@qq.com |
| hanmeimei | han@126.com |
+-----------+--------------+
3 rows in set (0.00 sec)

mysql> select uname ,position('@' in email) from email;
+-----------+------------------------+
| uname | position('@' in email) |
+-----------+------------------------+
| zhangsan | 5 |
| lilie | 3 |
| hanmeimei | 4 |
+-----------+------------------------+
3 rows in set (0.00 sec)

mysql> select uname ,right(email,position('@' in email)) from email;
+-----------+-------------------------------------+
| uname | right(email,position('@' in email)) |
+-----------+-------------------------------------+
| zhangsan | 3.com |
| lilie | com |
| hanmeimei | .com |
+-----------+-------------------------------------+
3 rows in set (0.00 sec)

mysql> select uname ,right(email,char_length(email)-position('@' in email)) from email;
+-----------+--------------------------------------------------------+
| uname | right(email,char_length(email)-position('@' in email)) |
+-----------+--------------------------------------------------------+
| zhangsan | 163.com |
| lilie | qq.com |
| hanmeimei | 126.com |
+-----------+--------------------------------------------------------+
3 rows in set (0.00 sec)

mysql> select uname ,right(email,length(email)-position('@' in email)) from email;
+-----------+---------------------------------------------------+
| uname | right(email,length(email)-position('@' in email)) |
+-----------+---------------------------------------------------+
| zhangsan | 163.com |
| lilie | qq.com |
| hanmeimei | 126.com |
+-----------+---------------------------------------------------+
3 rows in set (0.00 sec)

mysql> #截取邮箱
mysql> #截取邮箱后半部分;
mysql> select uname ,right(email,length(email)-position('@' in email)) from email;
+-----------+---------------------------------------------------+
| uname | right(email,length(email)-position('@' in email)) |
+-----------+---------------------------------------------------+
| zhangsan | 163.com |
| lilie | qq.com |
| hanmeimei | 126.com |
+-----------+---------------------------------------------------+
3 rows in set (0.00 sec)

mysql> #日期时间函数,取当前时间
mysql> select now;
ERROR 1054 (42S22): Unknown column 'now' in 'field list'
mysql> select now();
+---------------------+
| now() |
+---------------------+
| 2019-10-15 20:00:44 |
+---------------------+
1 row in set (0.05 sec)

mysql> select curdate();
+------------+
| curdate() |
+------------+
| 2019-10-15 |
+------------+
1 row in set (0.01 sec)

mysql> # now()返回datetime格式,curdate返回date格式
mysql> select curtime();
+-----------+
| curtime() |
+-----------+
| 20:02:19 |
+-----------+
1 row in set (0.00 sec)

mysql> #查看某一日是那一周的第几天
mysql> select dayofweek('2019-10-15');
+-------------------------+
| dayofweek('2019-10-15') |
+-------------------------+
| 3 |
+-------------------------+
1 row in set (0.05 sec)

mysql> select week('2019-10-15');
+--------------------+
| week('2019-10-15') |
+--------------------+
| 41 |
+--------------------+
1 row in set (0.00 sec)

mysql> select week('2019-12-30');
+--------------------+
| week('2019-12-30') |
+--------------------+
| 52 |
+--------------------+
1 row in set (0.00 sec)

mysql> select week(curdate());
+-----------------+
| week(curdate()) |
+-----------------+
| 41 |
+-----------------+
1 row in set (0.00 sec)

mysql> select week('2019-12-31');
+--------------------+
| week('2019-12-31') |
+--------------------+
| 52 |
+--------------------+
1 row in set (0.00 sec)

mysql> #案例:name 
mysql> # overtime 日期
mysql> # 5 2019-9-1
mysql> # 6 2019-9-2
mysql> # 3 2019-9-3
mysql> # 报表统计,按星期统计加班时间 
mysql> create table jiaban(num int(10) ,time date);
Query OK, 0 rows affected (0.52 sec)

mysql> insert into jiaban values(3,"2019-9-1"),(4,'2019-9-2'),(5,"2019-9-3"),(6,'2019-9-10'),(19,'2019-9-18');
Query OK, 5 rows affected (0.15 sec)
Records: 5 Duplicates: 0 Warnings: 0

mysql> select * from jiaban;
+------+------------+
| num | time |
+------+------------+
| 3 | 2019-09-01 |
| 4 | 2019-09-02 |
| 5 | 2019-09-03 |
| 6 | 2019-09-10 |
| 19 | 2019-09-18 |
+------+------------+
5 rows in set (0.00 sec)

mysql> #按星期统计加班时间;
mysql> select sum(num), week(time) from jiaban ;
+----------+------------+
| sum(num) | week(time) |
+----------+------------+
| 37 | 35 |
+----------+------------+
1 row in set (0.02 sec)

mysql> select sum(num), week(time) from jiaban group by week(time);
+----------+------------+
| sum(num) | week(time) |
+----------+------------+
| 12 | 35 |
| 6 | 36 |
| 19 | 37 |
+----------+------------+
3 rows in set (0.00 sec)

mysql> select num, week(time) from jiaban group by week(time);
+------+------------+
| num | week(time) |
+------+------------+
| 3 | 35 |
| 6 | 36 |
| 19 | 37 |
+------+------------+
3 rows in set (0.00 sec)

mysql> select sum(num), week(time) from jiaban group by week(time);
+----------+------------+
| sum(num) | week(time) |
+----------+------------+
| 12 | 35 |
| 6 | 36 |
| 19 | 37 |
+----------+------------+
3 rows in set (0.00 sec)

mysql> select *, week(time) from jiaban;
+------+------------+------------+
| num | time | week(time) |
+------+------------+------------+
| 3 | 2019-09-01 | 35 |
| 4 | 2019-09-02 | 35 |
| 5 | 2019-09-03 | 35 |
| 6 | 2019-09-10 | 36 |
| 19 | 2019-09-18 | 37 |
+------+------------+------------+
5 rows in set (0.00 sec)

mysql> #加密函数,码得
mysql> #md5加密函数;
mysql> select md5('1');
+----------------------------------+
| md5('1') |
+----------------------------------+
| c4ca4238a0b923820dcc509a6f75849b |
+----------------------------------+
1 row in set (0.07 sec)

mysql> select md5('1');
+----------------------------------+
| md5('1') |
+----------------------------------+
| c4ca4238a0b923820dcc509a6f75849b |
+----------------------------------+
1 row in set (0.00 sec)

mysql> #md5是不可逆的
mysql> #流程h控制函数
mysql> #case 变量
mysql> 2 when 值 then 语句；
-> 3 when 值 then 语句；
-> 4 else 语句；
-> 5 end case；
-> \c
mysql> #if(gender=0,'优先','等待') as vip
mysql> ifnull
-> \c
mysql> #ifnull的用法,判断第一个表达式是否为null 如果为null 返回第2 个表达式的值
mysql> #如果不为null 返回自身,即表达式1
mysql> select ifnull('',a);
ERROR 1054 (42S22): Unknown column 'a' in 'field list'
mysql> select ifnull('','a');
+----------------+
| ifnull('','a') |
+----------------+
| |
+----------------+
1 row in set (0.00 sec)

mysql> select ifnull(null,'a');
+------------------+
| ifnull(null,'a') |
+------------------+
| a |
+------------------+
1 row in set (0.00 sec)

mysql> #系统调试函数
mysql> 
mysql> 
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)

mysql> #user返回用户及主机,判断自己的身份
mysql> #database(),返回当前操作的数据库名
mysql> select database();
+------------+
| database() |
+------------+
| test01 |
+------------+
1 row in set (0.00 sec)

mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.12 |
+-----------+
1 row in set (0.00 sec)

mysql> #vension() 返回数据库的版本
mysql> #时间的h格式化,优先在业务逻辑上使用,
mysql> #总结: where 条件中,对某列使用了函数,由此列的索引不发挥作用
mysql> #视图 view
mysql> view 将查询表当作临时表使用,
-> \c
mysql> # 查询每个栏目下商品的平均价格,并对平均价格取前三的栏目
mysql> select cat_id,avg(shop_price),count(goods_id) from goods group by cat_id;
+--------+-----------------+-----------------+
| cat_id | avg(shop_price) | count(goods_id) |
+--------+-----------------+-----------------+
| 4 | 2297.000000 | 3 |
| 8 | 75.333333 | 3 |
| 11 | 31.000000 | 2 |
| 3 | 1746.066667 | 15 |
| 2 | 823.330000 | 1 |
| 5 | 3700.000000 | 1 |
| 13 | 33.500000 | 2 |
| 15 | 70.000000 | 2 |
| 14 | 54.000000 | 2 |
+--------+-----------------+-----------------+
9 rows in set (0.10 sec)

mysql> select cat_id,avg(shop_price) as average,count(goods_id) from goods group by cat_id order by average desc limit 3 ;
+--------+-------------+-----------------+
| cat_id | average | count(goods_id) |
+--------+-------------+-----------------+
| 5 | 3700.000000 | 1 |
| 4 | 2297.000000 | 3 |
| 3 | 1746.066667 | 15 |
+--------+-------------+-----------------+
3 rows in set (0.00 sec)

mysql> select cat_id,avg(shop_price) as average,count(goods_id) from goods group by cat_id order by average asc limit 3 ;
+--------+-----------+-----------------+
| cat_id | average | count(goods_id) |
+--------+-----------+-----------------+
| 11 | 31.000000 | 2 |
| 13 | 33.500000 | 2 |
| 14 | 54.000000 | 2 |
+--------+-----------+-----------------+
3 rows in set (0.00 sec)

mysql> #取平均价格由高到底第三到第5的栏目
mysql> select cat_id,avg(shop_price) as average,count(goods_id) from goods group by cat_id order by average asc ;
+--------+-------------+-----------------+
| cat_id | average | count(goods_id) |
+--------+-------------+-----------------+
| 11 | 31.000000 | 2 |
| 13 | 33.500000 | 2 |
| 14 | 54.000000 | 2 |
| 15 | 70.000000 | 2 |
| 8 | 75.333333 | 3 |
| 2 | 823.330000 | 1 |
| 3 | 1746.066667 | 15 |
| 4 | 2297.000000 | 3 |
| 5 | 3700.000000 | 1 |
+--------+-------------+-----------------+
9 rows in set (0.00 sec)

mysql> select cat_id,avg(shop_price) as average,count(goods_id) from goods group by cat_id;
+--------+-------------+-----------------+
| cat_id | average | count(goods_id) |
+--------+-------------+-----------------+
| 4 | 2297.000000 | 3 |
| 8 | 75.333333 | 3 |
| 11 | 31.000000 | 2 |
| 3 | 1746.066667 | 15 |
| 2 | 823.330000 | 1 |
| 5 | 3700.000000 | 1 |
| 13 | 33.500000 | 2 |
| 15 | 70.000000 | 2 |
| 14 | 54.000000 | 2 |
+--------+-------------+-----------------+
9 rows in set (0.00 sec)

mysql> # 将结果集设为a a频繁用到,因此用到视图
mysql> # 表通过某种运算得到的影子
mysql> #如何创建视图,建视图的时候语法 create view 表名 as 查询语句;
mysql> create view state as select cat_id,avg(shop_price) as average,count(goods_id) from goods group by cat_id;
Query OK, 0 rows affected (0.27 sec)

mysql> show tables;
+------------------+
| Tables_in_test01 |
+------------------+
| a |
| b |
| boy |
| category |
| email |
| girl |
| goods |
| jiaban |
| m |
| mian |
| result |
| state |
| t |
| user |
+------------------+
14 rows in set (0.01 sec)

mysql> #多了一张state表
mysql> select * from state;
+--------+-------------+-----------------+
| cat_id | average | count(goods_id) |
+--------+-------------+-----------------+
| 4 | 2297.000000 | 3 |
| 8 | 75.333333 | 3 |
| 11 | 31.000000 | 2 |
| 3 | 1746.066667 | 15 |
| 2 | 823.330000 | 1 |
| 5 | 3700.000000 | 1 |
| 13 | 33.500000 | 2 |
| 15 | 70.000000 | 2 |
| 14 | 54.000000 | 2 |
+--------+-------------+-----------------+
9 rows in set (0.06 sec)


mysql> select * from state order by average limit 3;
+--------+-----------+-----------------+
| cat_id | average | count(goods_id) |
+--------+-----------+-----------------+
| 11 | 31.000000 | 2 |
| 13 | 33.500000 | 2 |
| 14 | 54.000000 | 2 |
+--------+-----------+-----------------+
3 rows in set (0.00 sec)

mysql> #视图一旦创建完毕,可以完全当表使用,
mysql> # 简化查询,复杂的统计,
mysql> #更清晰的权限控制
mysql> # 开放权限,但是不想开放密码字段,用视图
mysql> # 多表查询,分表时候用,将表头放在视图中;
mysql> #视图是表的影子,表与视图相互影响的关系
mysql> #表的数据变化,影响视图的变化,
mysql> #以此例,,此视图的数据不能更改,其数据来自shop_price的平均值
mysql> #视图是否能够增删改呢?
mysql> #某种情况下是可以删除的,11对应,即表的数据能够推出视图的数据,视图的数据能够推出表的数据
mysql> #删除视图即 drop table/view 表名/视图名
mysql> exit
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| bookstore |
| clouddb01 |
| clouddb02 |
| clouddb03 |
| information_schema |
| mydb |
| mysql |
| performance_schema |
| shop |
| ssm_crud |
| struts |
| student |
| sys |
| test |
| test01 |
+--------------------+
15 rows in set (0.18 sec)

mysql> use test01;
Database changed
mysql> #algorithm 
mysql> # merge ---合并查询语句
mysql> #tem
mysql> #temptable ---临时表
mysql> #undefined --未定义,由系统判断
mysql> #建一张简单的查询视图,不同临时表,只用y条件合并

mysql> create view v1 as select * from goods where shop_price>300;
Query OK, 0 rows affected (0.52 sec)

mysql> #查询视图
mysql> select goods_id ,goods_name ,shop_price from v1 where shop_price<500;
+----------+---------------+------------+
| goods_id | goods_name | shop_price |
+----------+---------------+------------+
| 8 | 飞利浦9@9v | 399.00 |
+----------+---------------+------------+
1 row in set (0.01 sec)

mysql> #总的条件是>300 <500;
mysql> #这个简单的查询还建立临时表的话,开销有点大;
mysql> #这是我们可以指定algorithm为merge
mysql> create algorithm=merge view v2 as select * from goods where shop_price>300;
Query OK, 0 rows affected (0.21 sec)

mysql> select goods_id ,goods_name ,shop_price from v2 where shop_price<500;
+----------+---------------+------------+
| goods_id | goods_name | shop_price |
+----------+---------------+------------+
| 8 | 飞利浦9@9v | 399.00 |
+----------+---------------+------------+
1 row in set (0.00 sec)

mysql> #有的时候必须建临时表,
mysql> #比如,每个栏目的平均商品价格
mysql> #比如每个栏目下的最高d价格的商品
mysql> create algorithm=temptable view v3 as select goods_id,cat_id,goods_name from goods order by cat_id asc ,goods_id desc;
Query OK, 0 rows affected (0.21 sec)

mysql> select * from v3 group by cat_id;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 16 | 2 | 恒基伟业g101 |
| 32 | 3 | 诺基亚n85 |
| 18 | 4 | 夏新t5 |
| 23 | 5 | 诺基亚n96 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 6 | 11 | 胜创kingmax内存卡 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 28 | 15 | 联通50元充值卡 |
+----------+--------+----------------------------------------+
9 rows in set (0.05 sec)

mysql> select * from v3;
+----------+--------+----------------------------------------+
| goods_id | cat_id | goods_name |
+----------+--------+----------------------------------------+
| 16 | 2 | 恒基伟业g101 |
| 32 | 3 | 诺基亚n85 |
| 31 | 3 | 摩托罗拉e8 |
| 24 | 3 | p806 |
| 22 | 3 | 多普达touch hd |
| 21 | 3 | 金立 a30 |
| 20 | 3 | 三星bc01 |
| 19 | 3 | 三星sgh-f258 |
| 17 | 3 | 夏新n7 |
| 15 | 3 | 摩托罗拉a810 |
| 13 | 3 | 诺基亚5320 xpressmusic |
| 12 | 3 | 摩托罗拉a810 |
| 11 | 3 | 索爱c702c |
| 10 | 3 | 索爱c702c |
| 9 | 3 | 诺基亚e66 |
| 8 | 3 | 飞利浦9@9v |
| 18 | 4 | 夏新t5 |
| 14 | 4 | 诺基亚5800xm |
| 1 | 4 | kd876 |
| 23 | 5 | 诺基亚n96 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 |
| 4 | 8 | 诺基亚n85原装充电器 |
| 3 | 8 | 诺基亚原装5800耳机 |
| 6 | 11 | 胜创kingmax内存卡 |
| 5 | 11 | 索爱原装m2卡读卡器 |
| 26 | 13 | 小灵通/固话20元充值卡 |
| 25 | 13 | 小灵通/固话50元充值卡 |
| 30 | 14 | 移动20元充值卡 |
| 29 | 14 | 移动100元充值卡 |
| 28 | 15 | 联通50元充值卡 |
| 27 | 15 | 联通100元充值卡 |
+----------+--------+----------------------------------------+
31 rows in set (0.00 sec)

mysql> drop view v3;
Query OK, 0 rows affected (0.27 sec)

mysql> create algorithm=temptable view v3 as select goods_id,cat_id,goods_name,shop_price from goods order by cat_id asc ,shop_price desc;
Query OK, 0 rows affected (0.31 sec)


mysql> select * from v3 ;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 32 | 3 | 诺基亚n85 | 3010.00 |
| 17 | 3 | 夏新n7 | 2300.00 |
| 9 | 3 | 诺基亚e66 | 2298.00 |
| 21 | 3 | 金立 a30 | 2000.00 |
| 24 | 3 | p806 | 2000.00 |
| 31 | 3 | 摩托罗拉e8 | 1337.00 |
| 10 | 3 | 索爱c702c | 1328.00 |
| 13 | 3 | 诺基亚5320 xpressmusic | 1311.00 |
| 11 | 3 | 索爱c702c | 1300.00 |
| 12 | 3 | 摩托罗拉a810 | 983.00 |
| 19 | 3 | 三星sgh-f258 | 858.00 |
| 15 | 3 | 摩托罗拉a810 | 788.00 |
| 8 | 3 | 飞利浦9@9v | 399.00 |
| 20 | 3 | 三星bc01 | 280.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 14 | 4 | 诺基亚5800xm | 2625.00 |
| 1 | 4 | kd876 | 1388.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 3 | 8 | 诺基亚原装5800耳机 | 68.00 |
| 4 | 8 | 诺基亚n85原装充电器 | 58.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 5 | 11 | 索爱原装m2卡读卡器 | 20.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 26 | 13 | 小灵通/固话20元充值卡 | 19.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 30 | 14 | 移动20元充值卡 | 18.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
| 28 | 15 | 联通50元充值卡 | 45.00 |
+----------+--------+----------------------------------------+------------+
31 rows in set (0.00 sec)

mysql> select * from v3 group by cat_id;
+----------+--------+----------------------------------------+------------+
| goods_id | cat_id | goods_name | shop_price |
+----------+--------+----------------------------------------+------------+
| 16 | 2 | 恒基伟业g101 | 823.33 |
| 22 | 3 | 多普达touch hd | 5999.00 |
| 18 | 4 | 夏新t5 | 2878.00 |
| 23 | 5 | 诺基亚n96 | 3700.00 |
| 7 | 8 | 诺基亚n85原装立体声耳机hs-82 | 100.00 |
| 6 | 11 | 胜创kingmax内存卡 | 42.00 |
| 25 | 13 | 小灵通/固话50元充值卡 | 48.00 |
| 29 | 14 | 移动100元充值卡 | 90.00 |
| 27 | 15 | 联通100元充值卡 | 95.00 |
+----------+--------+----------------------------------------+------------+
9 rows in set (0.03 sec)

mysql> #编码问题
mysql> #字符编码到字符集的映射
mysql> #gb2312,utf-8
mysql> #unicode 码表,----- utf-8 压缩文件的关系
mysql> #如何截取utf-8无乱码
mysql> #从头开始,取1个字节,
mysql> #通过位运算,计算连续的1的g个数
mysql> #如为0 截取1个
mysql> #如为n 则截取n个
mysql> gbk转为utf-8
-> \c
mysql> #jbk
mysql> #jbk 转unicode 在转utf-8
mysql> #乱码是怎么形成,编码和解码不统一
mysql> #转码过程字节丢失

mysql> create table tem(id int ,time datetime not null default now() );;
Query OK, 0 rows affected (0.95 sec)

ERROR: 
No query specified


mysql> desc tem;
+-------+----------+------+-----+-------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+-------------------+-------+
| id | int(11) | YES | | NULL | |
| time | datetime | NO | | CURRENT_TIMESTAMP | |
+-------+----------+------+-----+-------------------+-------+
2 rows in set (0.13 sec)


mysql> drop table tem;
Query OK, 0 rows affected (0.49 sec)

mysql> create table tem(id int(11) not null primary key ,name varchar(50) not null ,time datetime not null default now());
Query OK, 0 rows affected (0.39 sec)


mysql> insert into tem(id,name) values(1,"lili"),(2,"韩梅梅"),(3,"笑话"),(4,"哈哈");
Query OK, 4 rows affected (0.20 sec)
Records: 4 Duplicates: 0 Warnings: 0

mysql> select * from tem;
+----+-----------+---------------------+
| id | name | time |
+----+-----------+---------------------+
| 1 | lili | 2019-10-16 19:45:54 |
| 2 | 韩梅梅 | 2019-10-16 19:45:54 |
| 3 | 笑话 | 2019-10-16 19:45:54 |
| 4 | 哈哈 | 2019-10-16 19:45:54 |
+----+-----------+---------------------+
4 rows in set (0.00 sec)

mysql> delete from tem order by id desc limit 2;
Query OK, 2 rows affected (0.33 sec)

mysql> select * from tem;
+----+-----------+---------------------+
| id | name | time |
+----+-----------+---------------------+
| 1 | lili | 2019-10-16 19:45:54 |
| 2 | 韩梅梅 | 2019-10-16 19:45:54 |
+----+-----------+---------------------+
2 rows in set (0.00 sec)

mysql> select *,week(time) from tem;
+----+-----------+---------------------+------------+
| id | name | time | week(time) |
+----+-----------+---------------------+------------+
| 1 | lili | 2019-10-16 19:45:54 | 41 |
| 2 | 韩梅梅 | 2019-10-16 19:45:54 | 41 |
+----+-----------+---------------------+------------+
2 rows in set (0.01 sec)

mysql> #设置client 和connection的字符集
mysql> # set character_set_client=gbk;
mysql> # set character_set_connection=utf8
mysql> # set character_set_ressults=gbk;
mysql> # set character_set_results=gbk;
mysql> # 1366 字符编码问题
mysql> #大转小会丢失
mysql> #即 server> connection> client 编码范围
mysql> #client con results 都是hgbk
mysql> #client con results 都是gbk
mysql> #若三者都是gbk 则可以简写
mysql> # 即 set names gbk
mysql> #utf8中文截取无乱码
mysql> #存储引擎,
mysql> # innodb myisam innodb支持事务,
mysql> 
mysql> #start transaction;
mysql> commit;
Query OK, 0 rows affected (0.00 sec)

mysql> #commit;
mysql> #rollback;
mysql> exit