Question

Consider this simple PHP page:

<?php

  $db = new mysqli("localhost", "myuser", "mypwd", "mydb");
    if ($db->connect_error)
      // Dying sequence;

    // Executing query
    $qres = $db->multi_query("SET @rank = -1; SELECT * FROM (SELECT @rank := @rank + 1 as rank, field1, field2 FROM mytable WHERE field1 = 'value') AS T1 WHERE rank = 2;");
    $db->commit();
    if (!qres) {
      // Problems in query
      // Dying
      $db->close();
      return;
    }
    if (!($qres->num_rows == 1)) {
      // Error fetched
      $numrows = $qres->num_rows;
      $db->close();
      // Dying
      return;
    }

    // Returning
    echo "ALLOK";

    $db->close();

  ?>

Well, this does not work.
either if I use query or multi_query

Can you help me?

Answer 1

It looks like you just want to select the 3rd row from some table. Though the rank will be nondeterministic since you don’t specify an ORDER BY clause for that inner query.

You don’t need this variable and multiple queries to do that.

Use an offset in the LIMIT clause, along with an ORDER BY clause, instead.

SELECT field1, field2 FROM mytable WHERE field1 = 'value' ORDER BY something LIMIT 2,1