So, I tried the following
$sql="INSERT INTO $tbl_name(gamename, gamecode, region, mode, vmc, smb, hdd, usb, notes, comp)VALUES('$gamename', '$cleangc', '$region', '$mode', '$vmc', '$smb', '$hdd', '$usb', '$notes', '$comp')
ON DUPLICATE KEY UPDATE
gamename = IF(gamename = '', $gamename, gamename),
region = IF (gamename = '', $region, region),
mode = IF(gamename = '', $mode, mode),
vmc = IF(gamename = '', $vmc, vmc),
smb = IF(gamename = '', $smb, smb),
hdd = IF(gamename = '', $hdd, hdd),
usb = IF(gamename = '', $usb, usb),
notes = IF(gamename = '', $notes, notes),
comp = IF(gamename = '', $comp, comp)";
And it gives me
Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Hack - Part 1 - Infection, gamename), region = IF (gamename = '', U, region), mo' at line 3
Same deal with Arcticwarrio's suggestion. I tried changing a few things, but unable to overcome the syntax error.
@Old_Pendant you're correct in that it may not happen very often, though I'd just prefer previous entries to be safe, as I cannot control whether or not a visitor checks to see if a game has been added before adding it again and overwriting the previous entry with possibly less compatibility information.
How can I incorporate conditions using a SELECT query before an INSERT and ON DUPLICATE KEY UPDATE? I've yet to try anything like this. My experience with SQL is limited.