Question

MYSQL 5.1.52-community 我有一个250万行的大桌子：

我写了这个查询来解析数据：

SELECT DISTINCT a.id_dem FROM planning_demandes a 
        INNER JOIN planning_demandes b ON a.id_dem = b.id_dem 
        AND b.idrh IS NOT NULL 
        AND b.idrh <> 'férié' 
        AND b.idrh <> 'Pferié' 
        INNER JOIN planning_demandes c ON a.id_dem = c.id_dem 
        AND c.idrh IS NULL

执行时间超过100秒。

如何快速重写此请求？（使用agregates？我应该创建临时表）

THX

Answer 1

删除一个连接，这是多余的查询使用以下两种连接条件： a.id_dem = b.id_dem 和 a.id_dem = c.id_dem ，
所以这也必须是真的： b.id_dem = c.id_dem

SELECT DISTINCT b.id_dem 
FROM planning_demandes b 
JOIN planning_demandes c ON B.id_dem = c.id_dem 
WHERE
        b.idrh IS NOT NULL 
        AND b.idrh <> 'férié' 
        AND b.idrh <> 'Pferié' 
        AND c.idrh IS NULL

sql如何快速查询一个大的自联接表

1 个答案: