Mysql Group by 问题请教 - V2EX
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liunaijie
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Mysql Group by 问题请教

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  •   liunaijie 2019-09-13 09:28:00 +08:00 2950 次点击
    这是一个创建于 2224 天前的主题,其中的信息可能已经有所发展或是发生改变。

    对 mysql 中的 group by 执行流程不太了解,如果同时使用 where group by having 语句后他们的执行顺序是怎样的,画了一个流程图不知道对不对,请大家指教一下。

    2 条回复    2019-09-13 10:18:37 +08:00
    intermole
        1
    intermole  
       2019-09-13 09:49:43 +08:00 via iPhone
    先 where,然后再
    在 where 结果里 group by,然后在 group by 结果里 having
    yiyang1106
        2
    yiyang1106  
       2019-09-13 10:18:37 +08:00   2
    where---->group by----->having where 是在分组前对数据进行过滤(即操作原始数据),而 having 是对分组后的数据进行过滤
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