3

このような降順で結果を返すクエリがあります。

  comment     postid      name      userid    tempid
  ----------------------------------------------------- 
    c1          199        User1      123321    1
    c2          199        User1      123321    2
    c3          199        User1      123321    3
    c4          199        User1      123321    4
    c5          199        User1      123321    5
    c6          199        User1      123321    6
    c7          198        User1      123321    7
    c8          198        User1      123321    8
    c9          198        User1      123321    9
    c10         197        User1      123321    10
    c11         197        User1      123321    11
    c12         197        User1      123321    12
    c13         197        User1      123321    13
    c14         197        User1      123321    13
    c15         197        User1      123321    13
    c16         197        User1      123321    13

ここで、それぞれの上位 5 つのレコードを選択したいと思いpostidます。望ましい結果は次のようになります。

  comment     postid      name      userid    tempid
  ----------------------------------------------------- 
    c1          199        User1      123321    1
    c2          199        User1      123321    2
    c3          199        User1      123321    3
    c4          199        User1      123321    4
    c5          199        User1      123321    5
    c7          198        User1      123321    7
    c8          198        User1      123321    8
    c9          198        User1      123321    9
    c10         197        User1      123321    10
    c11         197        User1      123321    11
    c12         197        User1      123321    12
    c13         197        User1      123321    13
    c14         197        User1      123321    13

これが私のクエリです。

 DECLARE rangee INT;
 DECLARE uid BIGINT;

 SET @rangee = plimitRange * 10; 
 SET @uid    = puserid;

PREPARE STMT FROM
'
SELECT comments.comment,comments.postid,user.name,comments.userid,comments.tempid 
FROM
user
INNER JOIN comments ON user.userid=comments.userid
INNER JOIN posts ON posts.postID = comments.postid
 WHERE 
comments.postid <=  
(SELECT MAX(postid) FROM
 (
  SELECT wall.postid FROM wall,posts WHERE  
  wall.postid = posts.postid AND posts.userid=?
  ORDER BY wall.postid DESC LIMIT 10 OFFSET ?
 )sq1
)

AND
comments.postid >= 
(SELECT MIN(postid) FROM
 (
   SELECT wall.postid FROM wall,posts WHERE
   wall.postid = posts.postid AND posts.userid=?
   ORDER BY wall.postid DESC LIMIT 10 OFFSET ?
  )sq2
)

 AND
 posts.userid = ?
 ORDER BY comments.postid DESC,comments.tempid DESC;
'; 
EXECUTE STMT USING @uid,@rangee,@uid,@rangee,@uid;
DEALLOCATE PREPARE STMT;

どうすればこれを達成できますか?

4

1 に答える 1

3

サブクエリを使用して、すべてのレコード（コメント）の各グループ内のランク（投稿による）を含むテーブルを実体化する必要があります。次に、外部クエリで、目的の範囲内のランクを持つレコードのみをフィルタリングできます（たとえば[1,5]、上位5つ）。

-- select top 5 comments of each of the user's desired posts
SELECT   comments.comment,
         comments.postid,
         user.name,
         comments.userid,
         comments.tempid
FROM     user JOIN (
           -- rank comments on user's desired posts by grouping a self-join
           -- use index (postid, tempid) for performance
           SELECT      c1.*, COUNT(*) rank
           FROM        (
                         -- select user's posts within desired range
                         SELECT postid
                         FROM   (
                                  -- rank user's posts by grouping a self-join
                                  -- use index (userid, postid) for performance
                                  SELECT      p1.postid, COUNT(*) rank
                                  FROM        posts p1
                                    LEFT JOIN posts p2
                                           ON p1.userid = p2.userid
                                          AND p1.postid < p2.postid
                                  WHERE       p1.userid = @uid
                                  GROUP BY    p1.postid
                                ) ranked_posts
                         WHERE  rank BETWEEN @rangee + 1 AND @rangee + 10
                       ) interesting_posts
                  JOIN comments c1 USING (postid)
             LEFT JOIN comments c2
                    ON c1.postid = c2.postid
                   AND c1.tempid < c2.tempid
           GROUP BY c1.postid
         ) comments USING (userid)
WHERE    comments.rank BETWEEN 1 AND 5
ORDER BY postid DESC, tempid DESC
于 2012-10-23T15:22:47.207 に答える