Upon Further experimentation I have found the solution, sort of. Using PHPMyAdmin to play around with a SELECT statement I finally get the desired results. Now the problem I have is when I plug it in to the PHP page, I do not get the desired results.
Any and all help would be appreciated
$query = "SELECT SKY_Members.Callsign, NCO_CheckIn.* FROM SKY_Members LEFT JOIN NCO_CheckIn USING (callsign) WHERE EVENT_ID IS NULL OR EVENT_ID <> '20170308ZZ'";
NOTE: The above script works in PHPMyAdmin but not on my .php page