Question

How can I optimize this query? It seems there should be a much easier way to do this. The goal is that it will still be able to be readily turned into a delete statement.

SELECT * FROM team 
WHERE team_id IN (
                  SELECT team_id 
                  FROM (
                        SELECT team.team_id, (
                                              SELECT COUNT(*) 
                                              FROM signup 
                                              WHERE signup.team_id = team.team_id
                                             ) AS members 
                        FROM team, schedule, event 
                        WHERE team.schedule_id = schedule.schedule_id 
                        AND schedule.event_id = event.event_id
                        AND event.event_id =183) AS t 
                  WHERE members = 0
                 )

Answer 1

A quick glance at this query gives me this:

select
    t.*
from
    team t
    inner join schedule s on t.schedule_id = s.schedule_id
    inner join event e on s.event_id = e.event_id
    left outer join signup sp on t.team_id = sp.team_id
where
    e.event_id = 183
    and sp.team_id is null

It looked like you’re trying to find all teams that are in an event but are not in the signup table. Is this accurate?

Also, I wanted to note that it will be faster to do joins then a bunch of subqueries, especially if the subqueries depend on each row (in your case, they do).

Cheers,
Eric