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Microsoft Windows [版本 6.1.7601] 版权所有 (c) 2009 Microsoft Corporation。保留所有权利。 C:\Users\Administrator>mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 178 Server version: 5.5.37 MySQL Community Server (GPL) Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | test | +--------------------+ 2 rows in set (0.00 sec) mysql> use test Database changed mysql> show tables; +----------------+ | Tables_in_test | +----------------+ | a | | b | | boy | | category | | girl | | goods | | m | | mian | | result | | t | | user | +----------------+ 11 rows in set (0.00 sec) mysql> select * from user; +-----+-------+-----+ | uid | name | age | +-----+-------+-----+ | 1 | lisi | 89 | | 3 | lilei | 19 | | 2 | luky | 18 | +-----+-------+-----+ 3 rows in set (0.01 sec) 排序 user mysql> desc user; +-------+----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+----------------------+------+-----+---------+----------------+ | uid | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(20) | NO | | | | | age | smallint(5) unsigned | NO | | 0 | | +-------+----------------------+------+-----+---------+----------------+ 3 rows in set (0.21 sec) 创建一个表结构 tmp mysql> create table tmp( -> id int, -> name varchar(20) -> )charset utf8 engine myisam; Query OK, 0 rows affected (0.11 sec) 插入 tmp 值为 mysql> insert into tmp -> values -> (1,'liubei'), -> (2,null); Query OK, 2 rows affected (0.01 sec) Records: 2 Duplicates: 0 Warnings: 0 查询表结构 mysql> select * from tmp; +------+--------+ | id | name | +------+--------+ | 1 | liubei | | 2 | NULL | +------+--------+ 2 rows in set (0.00 sec) 查询liubei mysql> select * from tmp where name='liubei'; +------+--------+ | id | name | +------+--------+ | 1 | liubei | +------+--------+ 1 row in set (0.00 sec) 查询NULL,得不到想要的那个值 mysql> select * from tmp where name=null; Empty set (0.00 sec) mysql> select * from tmp where name!=null; Empty set (0.00 sec) mysql> select null = null; +-------------+ | null = null | +-------------+ | NULL | +-------------+ 1 row in set (0.00 sec) mysql> select 0=0; +-----+ | 0=0 | +-----+ | 1 | +-----+ 1 row in set (0.00 sec) mysql> select null != null; +--------------+ | null != null | +--------------+ | NULL | +--------------+ 1 row in set (0.00 sec) 重点where name is null; where name is not null; mysql> select * from tmp where name is null; +------+------+ | id | name | +------+------+ | 2 | NULL | +------+------+ 1 row in set (0.00 sec) mysql> select * from tmp where name is not null; +------+--------+ | id | name | +------+--------+ | 1 | liubei | +------+--------+ 1 row in set (0.00 sec) |
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