Pull all parent records with or without child record - if child record exists select latest record I'm building a table of ALL records on vacation watch which have not expired  and are not already scheduled for a visit 


Select the property information
Select the mapzone cars
Select the last time the property was checked


My problem is if the property has never been checked the record is not selected

The code is:

FROM vacation_watch_master
LEFT JOIN property 
    ON vacation_watch_master.MstrLink = property.MstrLink
LEFT JOIN property_map_carzone 
    ON property.MapZone = property_map_carzone.MAP_ZONE
LEFT JOIN vac_watch_check_dates v1 
    ON vacation_watch_master.VWLink = v1.VWLink
WHERE v1.VWDateLink = (SELECT max(VWDateLink) 
                       FROM vac_watch_check_dates
                       WHERE vac_watch_check_dates.VWLink = vacation_watch_master.VWLink
                      )
HAVING vacation_watch_master.Watch_Expired  &gt; -1 
   AND vacation_watch_master.MstrLink NOT IN (
                              SELECT vac_watch_schedule.MstrLink 
                              FROM vac_watch_schedule
                                             )
In your WHERE clause, your v1.VMDateLink = SELECT MAX(VWDateLink) ... will not be true since the MAX will return NULL, and NULL is never equal to anything including NULL.

Try adding OR v1.VMDateLink IS NULL, but in general, I would create an inline view on vac_watch_check_dates with a single row per VWLink with the max VMDateLink.