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在写php语句中sql的写法有点混

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Release： 2016-06-23 13:34:37
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即where和having是否可以通用


回复讨论(解决方案)

where 是删选数据表的条件
having 是删选结果集的条件

经 where 删选后，结果集就可能会很小
having 只是再做一次筛选以挑出所需数据

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在写php语句中sql的写法有点混
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