sql query help

[bwaxse]

Alright so im pretty new to php and sql - I know theres an easier way to do this:

I have Class IDs set in the Users Table and I want to get the Class Names by referencing the Classes table.
The if statements - If a user has a class entered in, look up that ID and set the $_SESSION[CLASS#] equal to that name.

<?php
                        if ($_SESSION['CLASS1'] != "0"){
        $query2 = "SELECT sClassName FROM tbl_classes WHERE sClassID ='".$_SESSION['CLASS1']."'";
        $result2 = mysql_query($query2) or die("Invalid query: " . mysql_error());
        $row2 = mysql_fetch_assoc($result2);
       
        $_SESSION['CLASS1'] = $row2['sClassName'];}

        if ($_SESSION['CLASS2'] != "0"){
        $query3 = "SELECT sClassName FROM tbl_classes WHERE sClassID ='".$_SESSION['CLASS2']."'";
        $result3 = mysql_query($query3) or die("Invalid query: " . mysql_error());
        $row3 = mysql_fetch_assoc($result3);
       
        $_SESSION['CLASS2'] = $row3['sClassName'];}
X4 More times
?>

[fenway]

An IN clause would be most appropriate:

[code] "SELECT sClassName FROM tbl_classes WHERE sClassID IN ('".$_SESSION['CLASS1']."','".$_SESSION['CLASS2']."','".$_SESSION['CLASS3']."') ";[/code]

[bwaxse]

Thanks a bunch, I used:
$sql = "SELECT * FROM tbl_classes WHERE sClassID = '".$_SESSION['CLASS1']."'||'".$_SESSION['CLASS2']."'||'".$_SESSION['CLASS3']."'
||'".$_SESSION['CLASS4']."'||'".$_SESSION['CLASS5']."'||'".$_SESSION['CLASS6']."'";

Is there a major difference or is one better than the other?

[fenway]

Yes there is... the one you have shouldn't work!  You have to reference the column name as well with ORs.  I prefer using IN clauses because they make the intent of the query much clearer, and they can be optimized by the parser.