"北京"select * from user where address = null...">
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mysql中的不等于-ag真人游戏

多说无益,来个实例!!!

一个简单地表数据:

select * from user where address != "北京"
select * from user where address <> "北京"
select * from user where address = null
select * from user where address is null
select * from user where address != null
select * from user where address != "北京"
select * from user where address <> "北京"
select * from user where address = null
select * from user where address is null
select * from user where address != null
select * from user where address is not null

短短几条语句,三个极其常见的点,或许我们在回答的时候却不知所措,犹豫不决。

在<>和!=是等价的。在某字段不等于某值(非空的值)时,输出的结果此字段为空不输出。

is 和 is not 用于和 null 结合,我称它为不是,不是空 

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