如何从MySQL中的select中删除?

问题描述

此代码不适用于 MySQL 5.0，如何重新编写使其工作

This code doesn't work for MySQL 5.0, how to re-write it to make it work

DELETE FROM posts where id=(SELECT id FROM posts GROUP BY id  HAVING ( COUNT(id) > 1 ))

我想删除没有唯一 ID 的列.我会补充说，大多数时候它只有一个 id(我尝试了 in 语法，但它不起作用).

I want to delete columns that dont have unique id. I will add that most of the time its only one id(I tried the in syntax and it doesnt work as well).

推荐答案

SELECT(子)查询返回结果sets.因此，您需要在 WHERE 子句中使用 IN，而不是 =.

SELECT (sub)queries return result sets. So you need to use IN, not = in your WHERE clause.

另外，如this answer 您不能从同一查询中的子查询修改同一张表.但是，您可以在单独的查询中 SELECT 然后 DELETE，或者嵌套另一个子查询并为内部子查询结果设置别名(虽然看起来很笨拙):

Additionally, as shown in this answer you cannot modify the same table from a subquery within the same query. However, you can either SELECT then DELETE in separate queries, or nest another subquery and alias the inner subquery result (looks rather hacky, though):

DELETE FROM posts WHERE id IN (
    SELECT * FROM (
        SELECT id FROM posts GROUP BY id HAVING ( COUNT(id) > 1 )
    ) AS p
)

或者使用连接 按照 Mchl 的建议.

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