MySQL statement combining a join and a count?

Question

I\'ve got a table of \'folders\'. I want to return all the records with the userId of 16.

SELECT * FROM `folders` WHERE userId = 16;

I\'ve

Answer 1

SELECT  fol.*
 ,      (       SELECT  COUNT(*)
                FROM    files           fil
                WHERE   fil.Folder      = fol.Folder
        )       AS      "Files"
FROM    folders         fol
WHERE   fol.userId      = 16

It's called a correlated subquery.

http://dev.mysql.com/doc/refman/5.1/en/correlated-subqueries.html