I have a table containing email text for welcoming new users. There is a default email, one that may be client_id specific and one that may be user_id specific. I can do three queries to find user, then if not found. client, then if not found, default. But I'd prefer to have one query that selects the one that follows that priority list of user, client and default.
The other option is to do one query that may return up to three rows and then just select the appropriate row. But that is messy...
SELECT * FROM emails
OR (user_id IS NULL AND client_id=?)
OR (user_id IS NULL AND client_id IS NULL))
This may return up to three rows. Is there a way to just return one row?