I have a PostgreSQL database table called “user_links” which currently allows the following duplicate fields:
year, user_id, sid, cid
The unique constraint is currently the first field called “id”, however I am now looking to add a constraint to make sure the year, user_id, sid and cid are all unique but I cannot apply the constraint because duplicate values already exist which violate this constraint.
Is there a way to find all duplicates?