insert and update

[robinsnest]

Can anyone show me whats wrong with this code : If there isn't a row already with that members affid in it, then do the if, if there is a row already with the members affid in it, then just update it. IS the way i want, but of course its not working like that.

q("select * from referralamount where user_id=$affid");
$refm=00.10;
if($affid == ""){
	q("insert into referralamount (user_id, amount)values('$affid','refm')");
}else{
		 q("update referralamount set amount=amount+'$refm' where user_id='$affid'");
};

[robinsnest]

Ok it seems no matter what i do its not working right, it keeps inserting a new row, even though there is a row with the affid in it.
Only suppose to insert new row if the affid isnt in there.
I been trying different variations and no luck. I am not understanding something or code is all wrong

Can anyone help me out ..

$query = "select * from referralamount where user_id = '$affid' and amount = ''"; 
$result = mysql_query($query); 
$numrows = mysql_num_rows($result);
$refm=00.20;
if ($numrows == 0){ 
q("insert into referralamount (user_id, amount)values('$affid','$refm')");
}else{
	q("update referralamount set amount=amount+'$refm' where user_id='$affid'");
}