mysql 中 having和where子句的区别

1. having可以不与group by分组搭配使用

select name,age from user having age>18;
select name,age from user where age>18;

2.使用having时，select后必须选择having后出现的字段名

select name,age from user having age>18;
报错：
select name,age from user where sex='female';

3.聚合函数只能与having搭配使用

select name,agv(age) as ag from user having ag>18;

报错：
select name,agv(age) as ag，sex from user where ag>18 group by sex;