分组查询以及having使用

Group  by 注意事项：对查询的列有限制，除了聚合函数外，就必须是分组的项

order  by总是放在最后

代码示例：

select Gender as 性别 ,count (Gender) as 总和 from UserInfo

GROUP by Gender

备注：

Where和having的区别：

Where是在分组之前的查询，having是在分组之后的进行查询

order  by排序必须在最后

代码示例：

--分组查询 group by

select Gender as 性别, count (Gender) as 总和 from UserInfo

GROUP by Gender

orderby Gender desc

--如何对分组之后的结果进行筛选HAVING

select Gender as 性别,count(Gender) as 总和 from UserInfo

GROUP by Gender

having count(Gender)>6

order by Gender desc