在mysql中的不等于,<>,!=,is not
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
总结:
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