SELECt complaint.complaint_text, A.username, B.usernameFROM complaint LEFT JOIN user A ON A.user_id=complaint.opened_by LEFT JOIN user B ON B.user_id=complaint.closed_by

SELECt complaint.complaint_text, A.username, B.usernameFROM complaint LEFT JOIN user A ON A.user_id=complaint.opened_by LEFT JOIN user B ON B.user_id=complaint.closed_by