title: Trouble with 'order by' using a subtraction between dates (one of them comes from a query)
body: <p>I don't know if this is even possible, but I want to order the results of my query by the time passed between two dates, one of them coming from a query.</p>
  
  <p>What I want is to order the albums from DISCS so that the ones that have a REL_DATE closer to other date (given by the second query) appear first. The "SELECT ORDER_S..." query returns a single date extracted from another table and works fine by itself.</p>
  
  <pre><code>SELECT ALBUM
  FROM DISCS
  ORDER BY
    ABS((
    SELECT ORDER_S
    FROM SALE_LINE
    WHERE E_MAIL = (
      SELECT E_MAIL FROM CLIENTS
      WHERE DNI = 46470063
    ) AND ROWNUM = 1
    ORDER BY ORDER_S DESC)
    - REL_DATE) ASC;
  </code></pre>
  
  <p>Where ALBUM is a string type attribute, and ORDER_S and REL_DATE are DATE type attributes.</p>
  
  <p>However, all I get is an error on the <code>ORDER BY ORDER_S DESC)</code> line, "missing right parenthesis", and I can't figure out why.</p>