如何找到重复的字段组合 [英] How to find duplicate field combo

问题描述

我有一个包含 id、a 和 b 列的表.

I have a table with columns id, a, and b.

a+b 应该是唯一的，但这是一个没有正确约束的旧数据库.如何为 a+b 不唯一的记录获取一组 id?

a+b should be unique, but this is a legacy database that is not constrained correctly. How can I get a set of ids for records in which a+b is not unique?

如果我有

ID A B
1  2 3
2  2 3
3  1 3
4  1 4

然后我想从查询中取回记录 1 和 2.

Then I want to get records 1 and 2 back from the query.

推荐答案

select
    id, a, b

from your_table t

join (select a, b from your_table group by a, b having count(1) > 1) dup on dup.a = t.a and dup.b = t.b

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