mysql_fetch_array problem...!

I want to run a query to my db, fetching different fields from three different tables. In order to recognise the individual fields I give them names: select portal.portal as portal, portal.portalid as id... etc etc How can I refer to one specific row in this query..? What I mean is, how can i refer to result row number 4...? If I only selected rows from one table I could do something like this: $i = mysql_fetch_array($sql) ; echo "$i[4]" ;