SELECT a.ADID AS ghom_adstart
, b.ADID AS gint_adstart
, c.ADID AS gmig_adstart
, d.ADID AS gprx_adstart
FROM ghom_adstart AS a
LEFT JOIN gint_adstart as b ON a.ADID = b.ADID
LEFT JOIN gmig_adstart as c ON a.ADID = c.ADID
LEFT JOIN gprx_adstart as d ON a.ADID = d.ADID

UNION

SELECT a.ADID AS ghom_adstart
, b.ADID AS gint_adstart
, c.ADID AS gmig_adstart
, d.ADID AS gprx_adstart
FROM gint_adstart AS b
LEFT JOIN ghom_adstart as a ON a.ADID = b.ADID
LEFT JOIN gmig_adstart as c ON b.ADID = c.ADID
LEFT JOIN gprx_adstart as d ON b.ADID = d.ADID

UNION

SELECT a.ADID AS ghom_adstart
, b.ADID AS gint_adstart
, c.ADID AS gmig_adstart
, d.ADID AS gprx_adstart
FROM gmig_adstart AS c
LEFT JOIN gint_adstart as b ON c.ADID = b.ADID
LEFT JOIN ghom_adstart as a ON a.ADID = c.ADID
LEFT JOIN gprx_adstart as d ON c.ADID = d.ADID

UNION

SELECT a.ADID AS ghom_adstart
, b.ADID AS gint_adstart
, c.ADID AS gmig_adstart
, d.ADID AS gprx_adstart
FROM gprx_adstart AS d
LEFT JOIN gint_adstart as b ON d.ADID = b.ADID
LEFT JOIN gmig_adstart as c ON d.ADID = c.ADID
LEFT JOIN ghom_adstart as a ON a.ADID = d.ADID