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wysnylc

子查询比无查询更快?

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  •   wysnylc Sep 14, 2018 2033 views
    This topic created in 2787 days ago, the information mentioned may be changed or developed.

    第一张子查询 0.781s 第二张无子查询 2.958s 求解!谢谢!

    5 replies    2018-09-14 19:53:05 +08:00
    wysnylc
        1
    wysnylc  
    OP
       Sep 14, 2018
    删除 GROUP BY uid;分组条件后,两个 SQL 执行时间一致
    sagaxu
        2
    sagaxu  
       Sep 14, 2018 via Android   1
    建议先把查询条件改成一致的,不要一边用比较一边用 like。然后再 explain 比一下执行计划。
    wysnylc
        3
    wysnylc  
    OP
       Sep 14, 2018
    @sagaxu #2 ![]( )<br>
    ![]( )
    ![]( )
    第 1 张图为修改查询条件一致后执行时间
    2,3 为子查询和无子查询的执行计划
    xhystc
        4
    xhystc  
       Sep 14, 2018 via Android   1
    把子查询的 select 列表改成*试试
    wysnylc
        5
    wysnylc  
    OP
       Sep 14, 2018
    @xhystc #4 ![]( ) 把主表列改成*我也试过,效率应该跟列名无关
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