Mysql SQL的一些特殊用法记录

1、查询group by having 中having不起作用，及解决
直接上SQL：
需求是根据acontainer_number,aparentid分组后，数据大于1的数据，下面的语句竟不起作用。

//记录以前这样写是可以，不知为何现在不可以了
select acontainer_number,aparentid
from xxxxx_table
where acontainer_number is not null 
group by acontainer_number,aparentid
having count(*) > 1

解决方法：
只能再套一个子查询：

select acontainer_number,aparentid from (
select acontainer_number,aparentid
from xxxxx_table
where acontainer_number is not null 
group by acontainer_number,aparentid
) ag group by aparentid
having count(*) > 1

后面有时间再研究吧