sql group by 的having 与 where
2016-09-30 16:39
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最近一段时间已经连续两次遇到group by的问题,这次是第二次,是where与having用法问题。
在使用group by时:
where的作用是分组前筛选。也就是group by作用生效前,where会先排除掉不符合条件的数据。
having的作用是分组后筛选。也就是分组后通筛选符合条件的分组。
在使用group by时:
where的作用是分组前筛选。也就是group by作用生效前,where会先排除掉不符合条件的数据。
having的作用是分组后筛选。也就是分组后通筛选符合条件的分组。
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