sql语句实例 查询相关联的类别与空分类信息

SELECT
  cattmp.cl_to,
  cattmp.cl_count,
  user_name,
  log_timestamp,
  log_comment
FROM logging
JOIN `user` ON log_user = user_id
JOIN
(SELECT
   cl_to,
   COUNT(cl_to) AS cl_count
 FROM categorylinks
 LEFT JOIN page ON cl_to = page_title
 AND page_namespace = 14
 WHERE page_title IS NULL
 GROUP BY cl_to) AS cattmp
ON log_title = cattmp.cl_to
WHERE log_namespace = 14
AND log_type = "delete"
AND log_timestamp = (SELECT
                       MAX(log_timestamp)
                     FROM logging AS LAST
                     WHERE log_namespace = 14
                     AND cattmp.cl_to = LAST.log_title);

SELECT
  page_title,
  page_len
FROM categorylinks
RIGHT JOIN page ON cl_to = page_title
WHERE page_namespace = 14
AND page_is_redirect = 0
AND cl_to IS NULL
AND NOT EXISTS (SELECT
                  1
                FROM categorylinks
                WHERE cl_from = page_id
                AND cl_to = 'Wikipedia_category_redirects')
AND NOT EXISTS (SELECT
                  1
                FROM categorylinks
                WHERE cl_from = page_id
                AND cl_to = 'Disambiguation_categories')
AND NOT EXISTS (SELECT
                  1
                FROM templatelinks
                WHERE tl_from = page_id
                AND tl_namespace = 10
                AND tl_title = 'Empty_category');