Union based upon first query

[jgentes]

I have a query that I would like to use a union statement in to grab the number of replies to a specific thread. The initial topic thread is in a different table, which I am grabbing in the initial query... I would prefer to do this in the single query, however I supposed I could do a separate loops and grab the number of replies with a totally distinct query

SELECT id,title,category,message FROM forum UNION(SELECT count(msg_id) FROM forum_discussion WHERE msg_id=id) WHERE status!='Closed'

[Atli]

Couldn't you just use a sub-query?
Like:

SELECT 
  id, title, category, message
  ( SELECT COUNT(*) FROM forum_discussion
    WHERE msg_id = forum.id
  ) AS 'Posts'
FROM forum
WHERE status!='Closed'

[jgentes]

I tried that but it failed putting it just as a field.

if I ran just that query though and substituted the reference value for an actual value, it worked properly.