Question

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

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?

If I have

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

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

Answer 1

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