Re: I need Optimizaton of a Query - DISTINCT

[Rick James]

540x speedup -- even better than I would have guessed.

SELECT  DISTINCT u.id AS userid,
        IFNULL( c.id, a.catid ) AS catid,
        IFNULL( s.id, a.sectionid ) AS secid,
        a.id AS id,
        a.* ,                  -- some of this is duplicated
        a.introtext AS itext,
        a.fulltext AS mtext,
        u.name AS author,
        u.usertype,
        u.email AS authorEmail,
        a.created_by_alias AS authorAlias,
        a.created AS dsdate,
        c.name AS catName,
        CASE WHEN CHAR_LENGTH( a.alias ) THEN CONCAT_WS( ":", a.id, a.alias ) ELSE a.id END AS slug,
        CASE WHEN CHAR_LENGTH( c.alias ) THEN CONCAT_WS( ":", c.id, c.alias ) ELSE c.id END AS catslug
    FROM  
      ( SELECT  *            -- suggest listing only the rows needed
            FROM  jos_content
            WHERE  state = '1'
              AND  access <= 0
              AND  ( publish_up   = '0000-00-00 00:00:00' OR  publish_up   <= '2010-10-13 15:51:07' )
              AND  ( publish_down = '0000-00-00 00:00:00' OR  publish_down >= '2010-10-13 15:51:07' )
            ORDER BY  created DESC
            LIMIT  20 ) AS a
    LEFT JOIN  jos_users AS u ON u.id = a.created_by
    LEFT JOIN  `jos_categories` AS c ON c.id = a.catid
    LEFT JOIN  `jos_sections` AS s ON s.id = c.section
    WHERE  a.state = '1'
      AND  a.access <=0
      AND  ( c.access <=0 OR  a.sectionid =0 )
      AND  ( s.access <=0 OR  a.sectionid =0 )

That looks like the direction I was taking you.