forse
codice:
SELECT  t.id_category           AS category_id,
        t.id_user               AS user_id,
        t.subject, t.content,
        t.submitted, 
        t.status, 
        c.name                  AS category_name

FROM    tickets                 AS t,
        categories              AS c,
        users                   AS u
WHERE   u.id_workgroup='8'