Mach dir eine extra Variable für die KD, vielleicht auch eine extra Funktion dafür die dir das Zurückgibt.
stock Float:ReturnKD(playerid)
{
	if (PlayerInfo[playerid][kills] == 0 && PlayerInfo[playerid][deaths] == 0) return 0.0;	
	return PlayerInfo[playerid][kills] / PlayerInfo[playerid][deaths];
}
Und dann nutzt du:
public OnPlayerDisconnect(playerid,reason)
{
	if(GetPVarInt(playerid, "Logged") == 1)
	{
		format(Query, sizeof(Query), "UPDATE `playerinfo` SET `score` = '%d',`money` = '%d', `kills` = '%d', `deaths` = '%d',`kdratio` = '%f'  WHERE `user` = '%s'", GetPlayerScore(playerid), 	GetPlayerMoney(playerid), GetPVarInt(playerid, "killss"), GetPVarInt(playerid, "Deaths"), ReturnKD(playerid), escpname(playerid));
		mysql_query(Query);
	}
Ungetestet.
 
		 
		
		
	




