Unknown column in 'having clause'
<p>I need to find in sakila database the longest rental period of a movie.
I have tried this:</p>
<pre><code>  SELECT DISTINCT
      customer.first_name
    FROM
      rental,
      customer
    WHERE
      rental.customer_id = customer.customer_id
    GROUP BY
      rental.rental_id
    HAVING
      (
        rental.return_date - rental.rental_date
      ) =(
      SELECT
        MAX(countRental)
      FROM
        (
        SELECT
          (
            rental.return_date - rental.rental_date
          ) AS countRental
        FROM
          rental,
          customer
        GROUP BY
          rental.rental_id
      ) AS t1
    )
</code></pre>
<p>but I am getting the error:</p>
<pre><code># 1054 - Unknown column 'rental.return_date' in 'having clause'
</code></pre>
<p>Does anybody know why? I have used a column that's supposed to be the aggregated data. What am i missing?</p>