Sum function

I am looking for code that explains how to sum a value in a database based on a current field retrieved from the database. Example: query = "select course_name, course_build, milestone, testcase, time_tested, issue_status, comment, bug_number, tested_by, date_tested from testissues where test_issue_id = $viewid"; $result = mysql_query( $query ); 1 - retrieve needed fields from database based on the id the user links from ($viewid) 2 - assign the course_name value from the query statement to a variable to be used on html page Assign: $course_name = mysql_result( $result, 0, "course_name" ); Use variable: print " <td><font color = #006666><b>$course_name</b></font></td>\n"; Now I would like to sum ALL the time_tested values in my database WHERE the course_name = $course_name (the variable retrieved for the record) query = "select sum(time_tested) where course_name = $course_name"; $result = mysql_query( $query ); $total_time = mysql_result( $result, 0, "sum(time_tested)"); First issue -- php does not seem to recognize the value of $course_name Second issue -- will the $total_time value be calculated correctly based on the above syntax?