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having与where的区别?
1、where子句
对查询结果进行分组前,将不符合where条件的行去掉,即在分组之前过滤数据,即先过滤再分组。
where后面不可以使用聚合函数
2、having子句
having 子句的作用是筛选满足条件的组,即在分组之后过滤数据,即先分组再过滤。
having后面可以使用聚合函数。
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原文地址:https://www.cnblogs.com/ziyin/p/13953211.html
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