Check if Exist - Better Solution?

[lurn]

I have spent a few hours researching this just because I was curious and can't seem to find a good answer.  Normally I would do something like the following in PHP:

 

$query = "SELECT subd FROM tblsubd WHERE subd = '" & .$idstr. & "') ";
$result = mysql_query($query);
$num = mysql_num_rows($result);
if ($num != 0){
        }

 

The table only has 1 column so I just need to check if exist or not.  Seems like there has to be a better way.  Wouldn't the way I am doing it continue down the column even if it finds a result and search the whole column?  I am trying to avoid that if possible.

 

Thanks in advance so I can continue on.

 

 

 

[fenway]

If you're just checking to see if a given unique value exists, use count(*) and check mysql_num_rows().