MySql 从多列选择中删除？

Question

以下内容

delete from child N
where parent_id in
(select parent_id , count(*) c
from parent
group by other_attribute  having c > 1 )

可以理解的返回

Operand should contain 1 column(s)

如何解决这个问题？

Answer 1

您不需要在子查询中选择计数。只需在 HAVING 子句中显式使用计数即可:

delete from child N
where parent_id in
(
    select parent_id
    from parent
    group by other_attribute
    having count(*) > 1
)