MYSQL复习笔记4-基本SQL语句
Date: 20140115
Auth: Jin
参考：http://dev.mysql.com/doc/refman/5.1/zh/sql-syntax.html#select
一：数据库操作
1：显示数据库mysql> show databases;
2：创建数据库mysql> create database sky;
mysql> CREATE DATABASE sky CHARACTER SET utf8 COLLATE utf8_general_ci;
3：选择数据库mysql> use sky;
4: 查看当前数据mysql> select database();
5：删除数据库mysql> drop database sky;
6、修改数据名
修改数据库目录，貌似不是一个好方法
创建一个新库，然后dump管道导入新库，这个也是整库复制的方法
ALTER {DATABASE | SCHEMA} [db_name]
ALTER DATABASE用于更改数据库的全局特性。这些特性储存在数据库目录中的db.opt文件中
CHARACTER SET子句用于更改默认的数据库字符集。COLLATE子句用于更改默认的数据库校对集（COLLATE）
mysql> alter database dbtest CHARACTER SET utf8 COLLATE utf8_general_ci;
Query OK, 1 row affected (0.01 sec)
字符集介绍
http://blog.sina.com.cn/s/blog_9707fac301016wxm.html
mysql> show variables like '%character%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | latin1 |
| character_set_connection | latin1 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | latin1 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)
二：表结构操作
<一>基本表操作
1:显示数据表，需要先选择数据库
mysql> use mysql;
mysql> show tables;
2:创建数据表
mysql> use diege;
create table 表名 （字段1，字段2，…字段n,[表级约束] [Type|Engine=表类型|存储引擎]
其中字段格式为:
字段名 字段类型 [字段约束]
create table 表名 （字段名1 字段类型1 [字段约束]1，字段2，…字段n,[表级约束] [Type|Engine=表类型|存储引擎]
mysql> create table tb_name( -> id int(6) not null auto_increment, -> uname char(15) not null, -> sex bit default 1, -> birthday date not null default '1970-01-01', -> email varchar(20) default null, -> comment varchar(100), -> primary key(id), -> unique(uname) -> )ENGINE=Innodb default charset=utf8;
3 查看表结构
mysql> describe tb_name;
mysql> desc tb_name;
4:复制表
mysql> create table new_tb_name like tb_name;
5:根据已存在表的字段产生新表
SELECT vale1, value2 into Table2 from Table1
要求目标表Table2不存在，因为在插入时会自动创建表Table2，并将Table1中指定字段数据复制到Table2中。
Mysql不支持。SQL SERVER支持
MYSQL可用的方法
没有指定列
mysql> create table temp_diege select * from temp_username;
复制指定列的数据
mysql> create table temp_diege select username,ctime from log
mysql> create table testproduct select productId,pname from Product;
Query OK, 9 rows affected (5.00 sec)
Records: 9 Duplicates: 0 Warnings: 0
注意只复制，字段和数据，不会复制索引
比较：
Insert into Table2(field1,field2,...) select value1,value2,... from Table1
要求目标表Table2必须存在，由于目标表Table2已经存在，所以我们除了插入源表Table1的字段外，还可以插入常量。
6:删除表格
mysql> drop table new_tb_name;
<二>修改表操作
字段操作包括:add,drop,change,modify,
表操作rename（更改表名）
1. 改变表的名字
mysql> alter table tb_name1 rename tb_name2;
2. 增加列
alter table tb_name add col_name type
mysql> alter table tb_name add age smallint;
好像没办法同时添加两列
增加列并设置默认值
mysql> alter table tb_name add age smallint default 0;
增加列并设置为索引
mysql> alter table tb_name add age smallint not null primary key;
mysql> alter table tb_name add age smallint not null unique;
3. 删除列
alter table tbl_name drop col_name
mysql> alter table tb_name drop age;
4. 改变列名字
alter table tbl_name change old_col_name col_name
mysql> alter table tb_name change nianning age;
ERROR 1064 (42000): You have an error in your SQL syntax;
mysql> alter table tb_name change nianning age int(4);
必须要指定字段类型，原来什么字段就是什么字段即可
5. 改变列属性
方法1：
alter table tbl_name modify col_name type
mysql> alter table tb_name modify age int(2);
从smallint修改为int(2)
方法2
alter table tbl_name change old_col_name col_name type
mysql> alter table tb_name change age age smallint;
从int(2)修改为smallint
改变列名的同时改变属性
mysql> alter table tb30 change uname username varchar(30);
mysql> alter table tb_name change age nianning int(4);
6、改变列的属性，为字段添加默认值
字段已存在，不改变字段的名字和类型，只增加默认值
mysql> alter table tb_name modify age int(4) default 18;
必须要指定字段的类型
<三>修改表添加和删除索引
(一)添加新字段为为索引
也就是添加新字段，只不过约束为是索引
主键索引
mysql> alter table tb_name add uid int(11) not null primary key;
唯一索引
mysql> alter table tb1 add uname varchar(25) not null unique;
全文索引
mysql> alter table tb2 add fulltext(email);
ERROR 1214 (HY000): The used table type doesn't support FULLTEXT indexes
innodb不支持全文索引
普通索引
不知道怎么直接加，只有新加列再修改为普通索引
mysql> alter table tb1 add email varchar(50) not null;
mysql> alter table tb1 add index index_email(email);
多列索引-联合索引
先添加两列，然后两列组成联合索引
mysql> alter table tb1 add username varchar(50) not null;
mysql> alter table tb1 add uuid int(11) not null;
mysql> alter table tb1 add index un_index(uuid,username);
(二)修改原来的字段为索引
改变列的属性，将现有字段修改为索引
字段已存在，不改变字段的名字和类型，只是修改该字段为索引
PRIMARY KEY 主键索引-只可以添加一个，Key_name为PRIMARY
mysql>ALTER TABLE `table_name`add PRIMARY KEY（ `column` )
mysql> alter table tb1 add PRIMARY KEY(id);
UNIQUE 唯一索引-可以添加多个， Key_name为字段名，同一个子段都可以添加多次
mysql>ALTER TABLE `table_name`add UNIQUE（ `column` )
mysql> alter table tb1 add UNIQUE(uname);
FULLTEXT 全文索引 InnoDB 不支持全文索引
mysql>ALTER TABLE `table_name` add FULLTEXT（ `column` )
mysql> alter table tb1 add FULLTEXT(comment);
ERROR 1214 (HY000): The used table type doesn't support FULLTEXT indexes
INDEX 普通索引
mysql>ALTER TABLE `table_name` ADD INDEX index_name ( `column` )
mysql> alter table tb1 add index index_email(email);
多列索引-联合索引 联合索引本质上还是普通索引
mysql>ALTER TABLE `table_name` ADD INDEX index_name ( `column1`, `column2`, `column3` )
mysql> alter table tb1 add index index_union(id,uname);
注意：字段不用引号括起来
(三)查看索引
mysql> show index from tblname;
mysql> show keys from tblname;
mysql> show keys from tb1;
+-------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------
+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null |
Index_type | Comment |
+-------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------
+------------+---------+
| tb1 | 0 | PRIMARY | 1 | id | A | 0 | NULL | NULL | | BTREE
| |
| tb1 | 0 | uname | 1 | uname | A | 0 | NULL | NULL | | BTREE
| |
| tb1 | 1 | index_email | 1 | email | A | 0 | NULL | NULL | | BTREE
| |
| tb1 | 1 | index_union | 1 | id | A | 0 | NULL | NULL | | BTREE
| |
| tb1 | 1 | index_union | 2 | uname | A | 0 | NULL | NULL | | BTREE
| |
+-------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------
+------------+---------+
· Table
表的名称。
· Non_unique
如果MySQL索引不能包括重复词，则为0。如果可以，则为1。
· Key_name
索引的名称。#普通索引才可以指定列名称
· Seq_in_index
索引中的列序列号，从1开始。
· Column_name
列名称。
· Collation
列以什么方式存储在索引中。在MySQL中，有值‘A’（升序）或NULL（无分类）。
· Cardinality
MySQL索引中唯一值的数目的估计值。通过运行ANALYZE TABLE或myisamchk -a可以更新。基数根据被存储为整数的统计数据来计数，所以即使对于小型表，
该值也没有必要是精确的。基数越大，当进行联合时，MySQL使用该索引的机会就越大。
· Sub_part
如果列只是被部分地编入索引，则为被编入索引的字符的数目。如果整列被编入索引，则为NULL。
· Packed
指示关键字如何被压缩。如果没有被压缩，则为NULL。
· Null
如果列含有NULL，则含有YES。如果没有，则该列含有NO。
· Index_type
用过的索引方法（BTREE, FULLTEXT, HASH, RTREE）。
· Comment
(四)修改表删除索引
ALTER TABLE 'table_name' DROP INDEX index_name;
普通索引
mysql> alter table tb1 drop index index_email;
唯一索引【唯一索引也像普通索引一样删除】
mysql> alter table tb1 drop index uname;
主健索引
mysql> alter table tb1 drop PRIMARY KEY;
【注意】：如果主键索引是自增列是无法删除
三：处理表数据
insert,delete,update
准备演示的表
mysql> create table users ( -> id int(6) not null auto_increment, -> uname varchar(25) not null, -> sex bit default 0, -> birthday date default '1970-1-1', -> email char(35), -> department varchar(50), -> comment varchar(200) , -> PRIMARY KEY(id), -> UNIQUE(uname) -> )ENGINE=Innodb DEFAULT CHARSET=utf8; Query OK, 0 rows affected (0.04 sec) mysql> describe users; +------------+--------------+------+-----+------------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+------------+----------------+ | id | int(6) | NO | PRI | NULL | auto_increment | | uname | varchar(25) | NO | UNI | NULL | | | sex | bit(1) | YES | | b'0' | | | birthday | date | YES | | 1970-01-01 | | | email | char(35) | YES | | NULL | | | department | varchar(50) | YES | | NULL | | | comment | varchar(200) | YES | | NULL | | +------------+--------------+------+-----+------------+----------------+ 7 rows in set (0.00 sec)
1、插入记录 insert
Insert into 表名 (字段1，字段2,…) values (字段1的值，字段2的值，…)；
关键字value或者values都可以
插入必须字段，有默认值和自增列字段外的所有字段
mysql> insert into users (uname,email,department,comment) value ('diege','diege@foxmail.com','tech','a good boy');
mysql> select * from users;
+----+-------+------+------------+-------------------+------------+------------+
| id | uname | sex | birthday | email | department | comment |
+----+-------+------+------------+-------------------+------------+------------+
| 1 | diege | | 1970-01-01 | diege@foxmail.com | tech | a good boy |
+----+-------+------+------------+-------------------+------------+------------+
插入所有字段，插入所有字段就没有必要列出字段了
mysql> insert into users values (2,'lily',1,'1990-01-01','lily@foxmail.com','product','a good work');
mysql> select * from users where uname='lily';
+----+-------+------+------------+------------------+------------+-------------+
| id | uname | sex | birthday | email | department | comment |
+----+-------+------+------------+------------------+------------+-------------+
| 2 | lily | | 1990-01-01 | lily@foxmail.com | product | a good work |
+----+-------+------+------------+------------------+------------+-------------+
1 row in set (0.00 sec
一个insert插入多条记录
mysql> insert into users (uname,email,department,comment) value ('tom','tom@foxmail.com','tech','a good worker'),
('sum','sum@foxmail.com','product','a good boy')
2、删除记录 delete 和truncate
(1)清空表
mysql> delete from table_name;
mysql> truncate table_name;
两者区别
truncate 相当于drop table table_nam,然后再create table_name 速度快
delete from table_name; 是一条条记录删除
(2)根据条件删除
一般不会delete from table_name 删除数据，都会根据条件删除，所以要根据where子句约束删除的范围
mysql> delete from users where uname='lily';
mysql> delete from users where uname like 'lily%';
mysql> delete from users where id > 5;
mysql> delete from users where uname like 'tom%' and department='tech';
(3)同时删除多表记录
两张表：Product表和ProductPrice表。前者存在Product的基本信息，后者存在Product的价格。
mysql> create table Product ( -> productId intdesign(6) not null auto_increment, -> pname varchar(25) not null, -> created date default '2000-1-1', -> PRIMARY KEY(productId), -> UNIQUE(pname) -> )ENGINE=InnoDB DEFAULT CHARSET=utf8; mysql> create table ProductPrice ( -> productId int(6) not null, -> price int not null, -> PRIMARY KEY(productId) -> )ENGINE=InnoDB DEFAULT CHARSET=utf8;
插入测试数据
mysql> insert into Product(pname,created) values ('hat1','2000-11-25'),('hat2','2003-11-25'),('hat3','2008-06-25'),
('hat4','2010-08-08');
mysql> insert into Product(pname,created) values ('T-Shirts1','2004-06-15'),('T-Shirts2','2002-11-10'),('T-Shirts3','2000-03
-19'),('T-Shirts4','2013-07-15'),('T-Shirts5','2009-04-05')
mysql> select * from Product;
+-----------+-----------+------------+
| productId | pname | created |
+-----------+-----------+------------+
| 1 | hat1 | 2000-11-25 |
| 2 | hat2 | 2003-11-25 |
| 3 | hat3 | 2008-06-25 |
| 4 | hat4 | 2010-08-08 |
| 15 | T-Shirts1 | 2004-06-15 |
| 16 | T-Shirts2 | 2002-11-10 |
| 17 | T-Shirts3 | 2000-03-19 |
| 18 | T-Shirts4 | 2013-07-15 |
| 19 | T-Shirts5 | 2009-04-05 |
+-----------+-----------+------------+
mysql> insert ProductPrice values (1,100),(2,88),(3,150),(4,218),(15,190),(16,168),(17,218),(18,298),(19,398);
注意 这里的id没有外键约束
备份两份数据
mysql> create table ProductBak select * from Product;
mysql> create table ProductPriceBak select * from ProductPrice;
第一种跨表删除的方式是不用join，在delete时指定用半角逗号分隔多个表来删除，如下sql语句：
mysql> select a.*,b.* from Product as a,ProductPrice as b where a.productId=b.productId and a.created < '2004-01-01';
+-----------+-----------+------------+-----------+-------+
| productId | pname | created | productId | price |
+-----------+-----------+------------+-----------+-------+
| 1 | hat1 | 2000-11-25 | 1 | 100 |
| 2 | hat2 | 2003-11-25 | 2 | 88 |
| 16 | T-Shirts2 | 2002-11-10 | 16 | 168 |
| 17 | T-Shirts3 | 2000-03-19 | 17 | 218 |
+-----------+-----------+------------+-----------+-------+
mysql> select p.*, pp.* FROM Product p, ProductPrice pp WHERE p.ProductId = pp.productId AND p.created < '2004-01-01';
+-----------+-----------+------------+-----------+-------+
| productId | pname | created | productId | price |
+-----------+-----------+------------+-----------+-------+
| 1 | hat1 | 2000-11-25 | 1 | 100 |
| 2 | hat2 | 2003-11-25 | 2 | 88 |
| 16 | T-Shirts2 | 2002-11-10 | 16 | 168 |
| 17 | T-Shirts3 | 2000-03-19 | 17 | 218 |
+-----------+-----------+------------+-----------+-------+
4 rows in set (0.01 sec)
删除操作
DELETE p.*, pp.* FROM product p, productPrice pp WHERE p.productId = pp.productId AND p.created < '2004-01-01'
两张表都删除
mysql> delete a.*,b.* from Product as a,ProductPrice as b where a.productId=b.productId and a.created < '2004-01-01';
确认
mysql> select a.*,b.* from Product as a,ProductPrice as b where a.productId=b.productId and a.created < '2004-01-01';
Empty set (0.00 sec)
两个表个删除4条
只删除其中一张表
用 p.created > '2004-01-01'; 做条件
mysql> select a.*,b.* from Product as a,ProductPrice as b WHERE a.ProductId = b.productId AND a.created > '2004-01-01';
+-----------+-----------+------------+-----------+-------+
| productId | pname | created | productId | price |
+-----------+-----------+------------+-----------+-------+
| 3 | hat3 | 2008-06-25 | 3 | 150 |
| 4 | hat4 | 2010-08-08 | 4 | 218 |
| 15 | T-Shirts1 | 2004-06-15 | 15 | 190 |
| 18 | T-Shirts4 | 2013-07-15 | 18 | 298 |
| 19 | T-Shirts5 | 2009-04-05 | 19 | 398 |
+-----------+-----------+------------+-----------+-------+
上面如果除去一个相同的字段productId则为自然连接
已经删除ProductPrice以为例
mysql> delete b.* from Product as a,ProductPrice as b WHERE a.ProductId = b.productId AND a.created > '2004-01-01';
查询ProductPrice表
mysql> select * from ProductPrice;
Empty set (0.00 sec)
mysql> select * from Product;
+-----------+-----------+------------+
| productId | pname | created |
+-----------+-----------+------------+
| 3 | hat3 | 2008-06-25 |
| 4 | hat4 | 2010-08-08 |
| 15 | T-Shirts1 | 2004-06-15 |
| 18 | T-Shirts4 | 2013-07-15 |
| 19 | T-Shirts5 | 2009-04-05 |
+-----------+-----------+------------+
5 rows in set (0.00 sec)
第二种跨表删除的方式是使用inner join在join中指定两表之间的关联关系，如下sql语句：
mysql> select a.*,b.* from Product as a INNER JOIN ProductPrice as b ON a.productID = b.productID WHERE a.created < '2004-01
-01';
+-----------+-----------+------------+-----------+-------+
| productId | pname | created | productId | price |
+-----------+-----------+------------+-----------+-------+
| 1 | hat1 | 2000-11-25 | 1 | 100 |
| 2 | hat2 | 2003-11-25 | 2 | 88 |
| 6 | T-Shirts2 | 2002-11-10 | 6 | 168 |
| 7 | T-Shirts3 | 2000-03-19 | 7 | 218 |
+-----------+-----------+------------+-----------+-------+
4 rows in set (0.00 sec)
mysql> select p.*, pp.* FROM Product p INNER JOIN ProductPrice pp ON p.productId = pp.productId WHERE p.created < '2004
-01-01';
+-----------+-----------+------------+-----------+-------+
| productId | pname | created | productId | price |
+-----------+-----------+------------+-----------+-------+
| 1 | hat1 | 2000-11-25 | 1 | 100 |
| 2 | hat2 | 2003-11-25 | 2 | 88 |
| 6 | T-Shirts2 | 2002-11-10 | 6 | 168 |
| 7 | T-Shirts3 | 2000-03-19 | 7 | 218 |
+-----------+-----------+------------+-----------+-------+
INNER连接
关键字 A INNER JOIN B ON A.id=B.id
Product as a INNER JOIN ProductPrice as b ON a.productID = b.productID
DELETE p.*, pp.* FROM product p INNER JOIN productPrice pp ON p.productId = pp.productId WHERE p.created < '2004-01-01' mysql> delete a.*,b.* from Product as a INNER JOIN ProductPrice as b ON a.productID = b.productID WHERE a.created < '2004- 01-01';
确认
mysql> select a.*,b.* from Product as a INNER JOIN ProductPrice as b ON a.productID = b.productID WHERE a.created < '2004-
01-01';
Empty set (0.01 sec)
只删除一个表
这次我删除物品表格
mysql> select a.*,b.* from Product as a INNER JOIN ProductPrice as b ON a.productID = b.productID WHERE a.created > '2004-01
-01';
+-----------+-----------+------------+-----------+-------+
| productId | pname | created | productId | price |
+-----------+-----------+------------+-----------+-------+
| 3 | hat3 | 2008-06-25 | 3 | 150 |
| 4 | hat4 | 2010-08-08 | 4 | 218 |
| 5 | T-Shirts1 | 2004-06-15 | 5 | 190 |
| 8 | T-Shirts4 | 2013-07-15 | 8 | 298 |
| 9 | T-Shirts5 | 2009-04-05 | 9 | 398 |
+-----------+-----------+------------+-----------+-------+
mysql> delete b.* from Product as a INNER JOIN ProductPrice as b ON a.productID = b.productID WHERE a.created > '2004-01-01';
确认
mysql> select * from ProductPrice;
Empty set (0.00 sec)
mysql> select * from Product;
+-----------+-----------+------------+
| productId | pname | created |
+-----------+-----------+------------+
| 3 | hat3 | 2008-06-25 |
| 4 | hat4 | 2010-08-08 |
| 5 | T-Shirts1 | 2004-06-15 |
| 8 | T-Shirts4 | 2013-07-15 |
| 9 | T-Shirts5 | 2009-04-05 |
+-----------+-----------+------------+
5 rows in set (0.00 sec)
注意：跨表删除不必删除所有表的数据，上面的sql语句表会同时删除Product和ProductPrice两张表中的数据，但是你可以指定 DELETE
product.*从而只删除product表中的记录，
而不处理ProductPrice表中的记录。
跨表删除也可以使用left join，例如我们要删除所有在ProductPrice表中没有记录的Product表记录。如下sql语句：
DELETE p.*
FROM product p
LEFT JOIN productPrice pp
ON p.productId = pp.productId
WHERE pp.productId is null
3 修改记录 update
update tb_name set 字段=值1，子段2=值2 where 条件
1）修改单个记录
mysql> update users set uname='hellen' where id=2;
2)修改一个表的多条记录
mysql> update users set sex=1 where id>2;
Query OK, 3 rows affected (0.37 sec)
还是条件控制，条件控制一个还是多个，控制需要修改的记录范围
3）跨表修改多条记录
http://www.jb51.net/article/32648.htm
假定我们有两张表，一张表为Product表存放产品信息，其中有产品价格列Price；另外一张表是ProductPrice表，
我们要将ProductPrice表中的价格字段Price更新为Price表中价格字段的80%。
准备表
mysql> describe Product;
+-----------+-------------+------+-----+------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+------------+----------------+
| productId | int(6) | NO | PRI | NULL | auto_increment |
| pname | varchar(25) | NO | UNI | NULL | |
| created | date | YES | | 2000-01-01 | |
+-----------+-------------+------+-----+------------+----------------+
3 rows in set (0.00 sec)
mysql> describe ProductPrice;
+-----------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------+------+-----+---------+-------+
| productId | int(6) | NO | PRI | NULL | |
| price | int(11) | NO | | NULL | |
+-----------+---------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> alter table Product add price int(11) default 200;
mysql> update Product as a,ProductPrice as b set a.price=b.price where a.productId=b.productId;
Query OK, 9 rows affected (0.01 sec)
Rows matched: 9 Changed: 9 Warnings: 0
上面仅仅是准备数据，可以无视
mysql> select * from Product;
+-----------+-----------+------------+-------+
| productId | pname | created | price |
+-----------+-----------+------------+-------+
| 1 | hat1 | 2000-11-25 | 100 |
| 2 | hat2 | 2003-11-25 | 88 |
| 3 | hat3 | 2008-06-25 | 150 |
| 4 | hat4 | 2010-08-08 | 218 |
| 15 | T-Shirts1 | 2004-06-15 | 190 |
| 16 | T-Shirts2 | 2002-11-10 | 168 |
| 17 | T-Shirts3 | 2000-03-19 | 218 |
| 18 | T-Shirts4 | 2013-07-15 | 298 |
| 19 | T-Shirts5 | 2009-04-05 | 398 |
+-----------+-----------+------------+-------+
9 rows in set (0.00 sec)
假设Product中price 是总公司的产品定价，现在网络商务部要搞双11活到，所有商品8折，现在要修改对外显示的ProductPrice的表
方法1，类自然连接
mysql> update Product as a,ProductPrice as b set b.price=a.price*0.8 where a.productId=b.productId; Query OK, 9 rows affected (0.01 sec) Rows matched: 9 Changed: 9 Warnings: 0
确认
mysql> select * from ProductPrice;
+-----------+-------+
| productId | price |
+-----------+-------+
| 1 | 80 |
| 2 | 70 |
| 3 | 120 |
| 4 | 174 |
| 15 | 152 |
| 16 | 134 |
| 17 | 174 |
| 18 | 238 |
| 19 | 318 |
+-----------+-------+
9 rows in set (0.00 sec)
方法2 内连接 INNER JOIN on set
mysql> update Product as a INNER JOIN ProductPrice as b ON a.productId=b.productId set b.price=a.price*0.6 where a.created < '2004-01-01'; Query OK, 0 rows affected (0.01 sec) Rows matched: 4 Changed: 0 Warnings: 0
方法3 左外连接 left outer join #未实践
UPDATE product p
LEFT JOIN productPrice pp
ON p.productId = pp.productId
SET p.deleted = 1
WHERE pp.productId IS null
同时修改两个表
UPDATE product p INNER JOIN productPrice pp ON p.productId = pp.productId SET pp.price = pp.price * 0.8, p.dateUpdate = CURDATE() WHERE p.dateCreated < '2004-01-01';
