mysql – 如何优化此DB操作？

我对数据库很草率,无法使用连接,我甚至不确定会更快…

DELETE FROM atable 
WHERE  btable_id IN (SELECT id 
                     FROM   btable 
                     WHERE  param > 2) 
       AND ctable_id IN (SELECT id 
                         FROM   ctable 
                         WHERE  ( someblob LIKE '%_ID1_%' 
                                  OR someblob LIKE '%_ID2_%' )) 

Atable包含~19M行,这将删除~3M.目前,我只能使用LIMIT 100000运行查询,我不想整天坐在这里与phpmyadmin,因为每次删除(100.000行)运行约1.5分钟.

有什么方法可以加快/自动化它？

MySQL 5.5

(如果任何表包含20M行,你认为它已经是糟糕的数据库设计吗？)

解决方法:

使用EXISTS或JOIN代替IN来改善性能

使用EXISTS：

DELETE FROM Atable A 
WHERE EXISTS (SELECT 1 FROM Btable B WHERE A.Btable_id = B.id AND B.param > 2) AND 
      EXISTS (SELECT 1 FROM Ctable C WHERE A.Ctable_id = C.id AND (C.someblob LIKE '%_ID1_%' OR C.someblob LIKE '%_ID2_%'))

使用JOIN：

DELETE A 
FROM Atable A 
INNER JOIN Btable B ON A.Btable_id = B.id AND B.param > 2
INNER JOIN Ctable C WHERE A.Ctable_id = C.id AND (C.someblob LIKE '%_ID1_%' OR C.someblob LIKE '%_ID2_%')

标签：sql,mysql,sql-delete,join,exists
来源： https://codeday.me/bug/20190831/1773697.html