Número de comentários em posts, agrupado pela categoria. E o número de comentário no período anterior

wp_comments.sql

SET @startDate=DATE("2012-07-01");
SET @endDate:=DATE("2012-07-31");
SET @diff:=@diff:=DATEDIFF(@startDate, @endDate);
SET @previousStartDate:=ADDDATE(@startDate, @diff);
SET @previousEndDate:=ADDDATE(@endDate, @diff);

SELECT
    @startDate AS `currentStartDate`,
    @endDate AS `currentEndDate`,
    @previousStartDate AS `previousStartDate`,
    @previousEndDate `previousEndDate`,
    COUNT(*) AS `currentTotal`,
    (SELECT
        COUNT(*)
    FROM `wordpress`.`wp_comments` AS `c2`
    LEFT JOIN `wordpress`.`wp_posts` AS `p2` ON(`p2`.`ID`=`c2`.`comment_post_ID`)
    LEFT JOIN `wordpress`.`wp_term_relationships` AS `r2` ON(`r2`.`object_id`=`p2`.`ID`)
    LEFT JOIN `wordpress`.`wp_term_taxonomy` AS `x2` ON(`x2`.`term_taxonomy_id`=`r2`.`term_taxonomy_id`)
    LEFT JOIN `wordpress`.`wp_terms` AS `t2` ON(`t2`.`term_id`=`x2`.`term_id`)
    WHERE
        `t2`.`term_id`=`t`.`term_id` AND
        `c2`.`comment_date` BETWEEN
            @previousStartDate AND
            @previousEndDate
    GROUP BY `t2`.`term_id`) AS `previousTotal`,
    `t`.`name`
FROM `wordpress`.`wp_comments` AS `c`
LEFT JOIN `wordpress`.`wp_posts` AS `p` ON(`p`.`ID`=`c`.`comment_post_ID`)
LEFT JOIN `wordpress`.`wp_term_relationships` AS `r` ON(`r`.`object_id`=`p`.`ID`)
LEFT JOIN `wordpress`.`wp_term_taxonomy` AS `x` ON(`x`.`term_taxonomy_id`=`r`.`term_taxonomy_id`)
LEFT JOIN `wordpress`.`wp_terms` AS `t` ON(`t`.`term_id`=`x`.`term_id`)
WHERE 
    `c`.`comment_date` BETWEEN @startDate AND @endDate AND
    `x`.`taxonomy`="category"
GROUP BY `t`.`term_id`
ORDER BY `currentTotal` DESC, `previousTotal` DESC;

Nice. :-D