UPDATE vn.postCode pc
		LEFT JOIN vn.zoneGeo zg ON zg.id = pc.geoFk
	SET pc.geoFk = NULL
	WHERE zg.id IS NULL;

ALTER TABLE vn.postCode
	ADD CONSTRAINT postCode_zoneGeo_FK FOREIGN KEY (geoFk)
		REFERENCES vn.zoneGeo(id)
		ON DELETE RESTRICT
		ON UPDATE CASCADE;