Question

I’ve got a many-to-many accounts <-> users relationship. I’m trying to pull all the accounts shared by me and another user. So far I have something I modified from this answer:

SELECT * 
    FROM user
    JOIN account_user ON account_user.user_id = user.id
    JOIN account ON account.id = account_user.account_id
   WHERE user.id IN ({my_id},{other_user_id})
GROUP BY account.id
  HAVING COUNT(DISTINCT user.id) = 2

This seems to be on the right track, but the account_user table has a ‘role’ field, and I want to make sure that the record I get back contains the role of the other user, not mine. How would I tweak this to make that happen?

Answer 1

This works under my Oracle and the same basic idea should work under any DBMS:

SELECT account.*, role
FROM account
    JOIN account_user ON account_id = account.id AND user_id = :other_user_id
WHERE
    account.id IN (SELECT account_id FROM account_user WHERE user_id = :my_id)

In plain English:

• Join account and account_user for the other user.
• Accept only those accounts that are also connected to my user.

You can easily join user on top of that if you need to (as indicated by your SQL, but not by your question).