PHP/MySQL - Simple way to return a single value using mysql_result

Normally, we can use mysql_fetch_assoc to get the MySQL query result in PHP, example:
   $module_id = 2;
   $sql = "SELECT  * FROM  cesei_review_done WHERE module_id=$module_id";
    $result = mysql_query($sql,$db);
    while($row = mysql_fetch_assoc($result)) {
        $review_result = $row['review_done'];
    }
In some casews, we know MySQL will return only a single value, the simple way to get this single value is to use PHP function  mysql_result instead of  mysql_fetch_assoc, example:

   $module_id = 2;
   $sql = "SELECT  review_done FROM  cesei_review_done WHERE module_id=$module_id";
    $result = mysql_query($sql,$db);
    $review_result  = mysql_result($result, 0);