where

运算符 说明
= 等于
!= 不等于,某些数据库系统也写作 <>
> 大于
< 小于
>= 大于或等于
<= 小于或等于
BETWEEN … AND … 介于某个范围之内,例:WHERE age BETWEEN 20 AND 30
NOT BETWEEN …AND … 不在某个范围之内
IN(项1,项2,…) 在指定项内,例:WHERE city IN('beijing','shanghai')
NOT IN(项1,项2,…) 不在指定项内
LIKE 搜索匹配,常与模式匹配符配合使用
NOT LIKE LIKE的反义
IS NULL 空值判断符
IS NOT NULL 非空判断符
NOT、AND、OR 逻辑运算符,分别表示否、并且、或,用于多个逻辑连接。优先级:NOT > AND > OR
% 模式匹配符,表示任意字串,例:WHERE username LIKE '%user'
REGEXP 模式匹配符,表示任意字串,例:WHERE username LIKE '%user'
--测试条件
a = 'test'
table.a = 'test' and table.b != 'test' 
a > '3' or b < '5' or c >= '4' or d <= '5' 
a > '3' and (b < '5' or c = 10)
a > '3' and (b < '5' or c = 10 and (d = 10 or e = 13))
a like '%test%' or b is null  and c is not null
a not in (3,4,5) and b in (3,4,5)
a between '1' and '10' and b not bebween '1' and '13'
a REGEXP "^fo"