Question

我有一个删除查询，可以很好地处理少量行。但是现在大约有80K的行由于“超时”而失败了

我的两个桌子是这样的：

TableA
------

| Column     | type       |
|------------|------------|
| link_id    | bigint(40) |
| product_id | int(10)    |
| parent_id  | int(10)    |

Table B
-------

| Column    | type    |
|-----------|---------|
| id        | int(11) |
| parent_id | int(11) |
| child_id  | int(11) |

我这样查询以进行删除

DELETE FROM TABLEA
WHERE link_id IN (
    SELECT link_id FROM (
        SELECT link_id, parent_id, product_id FROM TABLEA
        UNION ALL
        SELECT id, parent_id, child_id FROM TABLEB
    ) tbl
    GROUP BY parent_id, product_id
    HAVING count(*) = 1
    ORDER BY parent_id
) ;

但谁不是最优化的人。

目标是从表A中删除表B中不存在的所有记录为“ parent_id / child_id”夫妇。

在表A中，“ product_id”列为“ child_id”。

谢谢

Answer 1

解决此问题的一种方法

DELETE A  FROM TABLEA A
INNER JOIN 
(    SELECT link_id FROM 
    (
        SELECT link_id, parent_id, product_id FROM TABLEA
        UNION ALL
        SELECT id, parent_id, child_id FROM TABLEB
    ) tbl
    GROUP BY parent_id, product_id
    HAVING count(*) = 1)B
ON A.link_id=B.link_id
where   A.link_id is not null;

Answer 2

我将使用NOT EXISTS来获取与tableb没有任何关系的link_id

DELETE FROM TABLEA
WHERE link_id IN (SELECT link_id 
                  FROM TABLEA a
                  where not exists (select link_id 
                                    from tableb b
                                    where b.parent_id=a.parent_id and b.child_id=a.product_id))

删除查询优化

2 个答案: