Concat two columns from different MySQL tables <p>I am trying to concat a list of usernames into one column in MySQL. The two lists of usernames are coming from two different tables. </p> <pre><code>(SELECT CAST(group_concat(CONCAT(usr.username, ' ' ,cc.username)separator ',') AS CHAR(200)) FROM messagejobrecipients mr LEFT JOIN chatusers cur on mr.ChatUserID = cur.ID left join users usr on cur.TableUserID=usr.user_id left join customer_contacts cc on cur.TableUserID=cc.id WHERE JobID = j.ID) AS MembersIncluded </code></pre> <p>The code works fine if I just try to display <code>CONCAT(usr.username)</code> or <code>CONCAT(cc.username)</code> but when I try display both <code>CONCAT(usr.username, ' ' ,cc.username)</code> it always returns null. </p>