在php在线考试系统中由rand使用订单时重复出现问题

Question

Questions are repeating when used order by rand in php online exam system

if(isset($_SESSION['stdname'])){
    $result=executeQuery("select stdanswer,answered from studentquestion where stdid=".$_SESSION['stdid']." and testid=".$_SESSION['testid']." and qnid=".$_SESSION['qn'].";");
    $r1=mysql_fetch_array($result);
    $result=executeQuery("select * from question where testid=".$_SESSION['testid']." and qnid=".$_SESSION['qn']."order by rand();");
    $r=mysql_fetch_array($result);

Answer 1

Use the key word DISTINCT in your query.

$result=executeQuery("select DISTINCT * from question where testid=".$_SESSION['testid']." and qnid=".$_SESSION['qn']." order by rand();");

Also mysql_* is deprecated. Follow @Magnus's comment

Answer 2

Instead of using "ORDER BY RAND" in the query, grab all the possible questions. Once you've got the questions into an array, use the shuffle() function ( http://php.net/manual/en/function.shuffle.php ) to randomise the questions. Then all you need to do is use a for loop to get the required number of questions.