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mysql> select * from user; +------+----------+-----------+ | id | name | address | +------+----------+-----------+ | 1 | xiaoming | beijing | | 2 | xiaobai | shandong | | 3 | x...
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posted @ 2019-08-07 02:06
anobscureretreat
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mysql> select * from test -> ; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | ...
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posted @ 2019-08-07 01:55
anobscureretreat
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mysql> select * from test; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xia...
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posted @ 2019-08-07 01:30
anobscureretreat
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mysql> select * from test; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xia...
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posted @ 2019-08-07 00:00
anobscureretreat
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mysql> select * from user; +------+----------+-----------+ | id | name | address | +------+----------+-----------+ | 1 | xiaoming | beijing | | 2 | xiaobai | shandong | | 3 | x...
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posted @ 2019-08-06 23:38
anobscureretreat
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mysql> select * from user; +------+----------+-----------+ | id | name | address | +------+----------+-----------+ | 1 | xiaoming | beijing | | 2 | xiaobai | shandong | | 3 | x...
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posted @ 2019-08-06 15:46
anobscureretreat
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mysql> select * from test; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xia...
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posted @ 2019-08-06 14:44
anobscureretreat
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mysql> select rtrim(" cdcdcd "); +--------------------+ | rtrim(" cdcdcd ") | +--------------------+ | cdcdcd | +--------------------+ 1 row in set (0.00 sec)
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posted @ 2019-08-06 12:52
anobscureretreat
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mysql> select upper(" cdcdcd"); +------------------+ | upper(" cdcdcd") | +------------------+ | CDCDCD | +------------------+ 1 row in set (0.00 sec)
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posted @ 2019-08-06 12:48
anobscureretreat
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mysql> select right(" dedede",6); +---------------------+ | right(" dedede",6) | +---------------------+ | dedede | +---------------------+ 1 row in set (0.00 sec) mysql> select rig...
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posted @ 2019-08-06 12:47
anobscureretreat
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mysql> select " DFREF"; +--------+ | DFREF | +--------+ | DFREF | +--------+ 1 row in set (0.00 sec) mysql> select lower(" DFREF"); +-----------------+ | lower(" DFREF") | +-----------------+ | ...
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posted @ 2019-08-06 12:17
anobscureretreat
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mysql> select " dedede"; +----------+ | dedede | +----------+ | dedede | +----------+ 1 row in set (0.00 sec) mysql> select ltrim(" dedede"); +-------------------+ | ltrim(" dedede") | +-...
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posted @ 2019-08-06 12:00
anobscureretreat
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mysql> select * from test; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xia...
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posted @ 2019-08-06 11:42
anobscureretreat
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mysql> select * from test; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xia...
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posted @ 2019-08-06 11:26
anobscureretreat
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mysql> select * from test; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xia...
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posted @ 2019-08-06 11:12
anobscureretreat
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mysql> select * from test; +----+------------+-------+-----------+ | id | name | score | subject | +----+------------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xia...
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posted @ 2019-08-06 10:59
anobscureretreat
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字符类 [:alnum:]=[a-zA-Z0-9] [:alpha:]=[a-zA-Z] [:digit:]=[0-9] [:lower:]=[a-z] [:upper:]=[A-Z] [:xdigit:]=[a-fA-F0-9] 重复元字符 * = >=0 + = >=1 = {1,} ? = {0,1} {n} 指定数目 {n,} = >=n {n,m} = >=n...
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posted @ 2019-08-06 01:55
anobscureretreat
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mysql> select concat(name,"**",id) as test from test; +----------------+ | test | +----------------+ | xiaoming**1 | | xiaohong**2 | | xiaohong**3 | | xiaohong**4 | | xiaohong...
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posted @ 2019-08-06 01:40
anobscureretreat
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mysql> select " ddd dddee "; +--------------+ | ddd dddee | +--------------+ | ddd dddee | +--------------+ 1 row in set (0.00 sec) mysql> select rtrim(" ddd dddee "); +------------------...
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posted @ 2019-08-06 01:33
anobscureretreat
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mysql> select * from test; +----+----------+-------+-----------+ | id | name | score | subject | +----+----------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xiaohong | ...
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posted @ 2019-08-06 00:54
anobscureretreat
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mysql> select * from test; +----+----------+-------+-----------+ | id | name | score | subject | +----+----------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xiaohong | ...
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posted @ 2019-08-06 00:44
anobscureretreat
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mysql> select * from test; +----+----------+-------+-----------+ | id | name | score | subject | +----+----------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xiaohong | ...
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posted @ 2019-08-06 00:14
anobscureretreat
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mysql> select * from test; +----+----------+-------+-----------+ | id | name | score | subject | +----+----------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xiaohong | ...
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posted @ 2019-08-05 22:40
anobscureretreat
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posted @ 2019-08-05 22:03
anobscureretreat
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mysql> select * from test; +----+----------+-------+-----------+ | id | name | score | subject | +----+----------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xiaohong | ...
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posted @ 2019-08-05 21:38
anobscureretreat
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mysql> select * from test; +----+----------+-------+-----------+ | id | name | score | subject | +----+----------+-------+-----------+ | 1 | xiaoming | 89 | shuxue | | 2 | xiaohong | ...
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posted @ 2019-08-05 21:33
anobscureretreat
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16进制转8进制 8进制数转换为10进制数 8进制数转换为16进制数 https://www.runoob.com/php/func-math-base-convert.html
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posted @ 2019-08-05 19:50
anobscureretreat
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我们仅在第一次调用 strtok() 函数时使用了 string 参数。在首次调用后，该函数仅需要 split 参数，这是因为它清楚自己在当前字符串中所在的位置。 如需分割一个新的字符串，请再次调用带 string 参数的 strtok() 参考： https://www.w3school.com.
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posted @ 2019-08-05 19:25
anobscureretreat
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%匹配任意长度 _ 匹配单个字符
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posted @ 2019-08-05 01:04
anobscureretreat
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mysql> select * from table1; +----------+------------+-----+---------------------+-------+ | name_new | transactor | pid | order_date | price | +----------+------------+-----+-------------...
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posted @ 2019-08-04 23:45
anobscureretreat
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假设id为主键，id可以保证字段数据唯一性，但是一张表只有一个主键。主键的值：修改成的0，可以存在，就是排个序。新添加的0，不允许存在，要根据行号改变。本身存在的0，不允许存在，要从1开始递增变化。Insert 进去 id = 0的数据，数据会从实际的行数开始增加 参考： https://www.c
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posted @ 2019-08-04 23:27
anobscureretreat
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唯一键特点： 1、唯一键在一张表中可以有多个。 2、唯一键允许字段数据为NULL，NULL可以有多个（NULL不参与比较） //一个表中允许存在多个唯一键,唯一键允许为空,在不为空的情况下,不允许重复 //设置一个字段为唯一键 mysql> alter table `table1` add unique ( `name_new`); Query OK, 0 rows affected (0.0...
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posted @ 2019-08-04 23:25
anobscureretreat
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//不允许为null alter table table1 change id id int(10) not null; //允许为null alter table table1 change id id int(10) null; //name_new允许为空 insert table1(id,transactor) values(1,"world"); //transactor...
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posted @ 2019-08-04 23:21
anobscureretreat
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mysql> alter table table1 add price int(10) not null; Query OK, 0 rows affected (0.05 sec) Records: 0 Duplicates: 0 Warnings: 0 //删除一个字段 ALTER TABLE table1 drop id;
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posted @ 2019-08-04 23:20
anobscureretreat
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//修改字段长度 alter table table1 modify name char(15); //修改字段名称以及长度 alter table table1 change name name_new char(32); alter table table1 change id id int(10);
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posted @ 2019-08-04 23:18
anobscureretreat
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//重命名表 rename table table1 to table2; //重命名多个表 rename table table1 to table2,table3 to table4,table5 to table6;
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posted @ 2019-08-04 23:16
anobscureretreat
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//创建数据库 create database testdata; //切换数据库 use testdata; //创建表 create table table1(id int,name varchar(10)); //插入值 insert table1(id,name) values(1,"xiaoming");
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posted @ 2019-08-04 23:15
anobscureretreat
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//offset参数指定要返回的第一行的偏移量。第一行的偏移量为0，第二行的偏移量为1。count指定要返回的最大行数。LIMIT offset,count;
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posted @ 2019-08-04 23:08
anobscureretreat
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posted @ 2019-08-04 22:55
anobscureretreat
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默认不指定，order by 按照升序排列。 asc：升序 desc：降序
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posted @ 2019-08-04 22:46
anobscureretreat
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