In one table but NOT in the other ?
I have two tables: PLATFORMS and MAIN
I want to select the platform id numbers that exist in PLATFORMS
but that have not yet been used in MAIN
In PLATFORMS the platform id number field is platform_id
and in MAIN, if the platform has been used, its id is in platform_no
This gives me ALL the platform names and ids:
but how do I exclude all those already used in MAIN ???
$sql_plat = "SELECT platform_id,plat_name FROM PLATFORMS ";
$result_plat = mysql_query($sql_plat) or die("could not find platforms". mysql_error());
Thanks for advice.