Probably an easy question - blank search fields (PHP & MySQL)

Hiya, I'm writing a backend in MySQL with a PHP frontend. One of the PHP pages searches the database. The user can enter as many or as few fields as they like. I then search the database using this code: $result = mysql_query("select * from equipment where (category='$category') and (description like '$description') and (roomloc='$roomloc') and (quantity like '$quantity') and (serialno like '$serialno') and (patdue like '$patdue')",$db); Messy, I know. The category and roomloc are <option>s and therefore are definite. However, if the user enters nothing for the other fields, they get given no results. If I set the default value of each field to % in the page that calls this, then it works fine. It's just not what I'd like to do - have the user clear out % from each field before putting their data in. Is there an easy way to code "if the field is blank, send %, else send the users entry" or just putting % before whatever is sent? (this shouldn't mess up what's being entered, surely?) Thanks for any help. -- Gary Smith E: shadyron@l33t-d00d.co.uk W: http://www.l33t-d00d.co.uk Pics: http://photos.l33t-d00d.co.uk