如何在mysql / php中为插入查询添加序列号是。 不是auto_increment

Question

I would like to insert a sequencial item number when everytime the user creates an exam. everytime he creates an exam it restarts to 1. I extremely need your help, people. More power. :)

here is my code:

$examid = $_SESSION['examid'];
$itemnum = 1;

$sql = mysql_query("INSERT INTO exam_questions (question_description, question_type, question_exam_id) VALUES ('$question', '$type', '$examid')")or die(mysql_error());
$lastinsertid = mysql_insert_id();
mysql_query("UPDATE exam_questions SET question_set_id='<??????????>' WHERE question_id='$lastinsertid' LIMIT 1")or die(mysql_error());

Answer 1

Try doing this with a join:

UPDATE exam_questions eq cross join
       (select max(question_set_id) as qsi
        from exam_questions
        where question_id='$lastinsertid'
       ) as const
    SET eq.question_set_id = const.qsi + 1
    WHERE question_id='$lastinsertid';