mysql 分组和聚合函数

Mysql 聚集函数有5个：

1、COUNT() 记录个数（count(1),count(*)统计表中行数，count(列名)统计列中非null数）

2、MAX() 最大值

3、MIN() 最小值

4、AVG()平均值

5、SUM() 求和

聚集函数常常和分组一起工作。

1、创建分组

select name, max(age) from stu group by name;

2、过滤分组

select name, max(age) from stu group by name having min(age) >10;

3、分组排序

select name, max(age) from stu group by name having min(age) >10 order by max(age) asc;

select name, max(age) from stu group by name having min(age) >10 order by max(age) desc limit 1,5;