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1 つのクエリで最後の投稿者をすべて選択し、配列に格納するフォーラム システムの最適化を試みています。問題は、データベースが予期しない結果を返していることです

PHP バージョン 5.3.13

MySQL バージョン 5.1.63

$getPosts = $dB->fetch('
  SELECT
    post_id, post_poster_id, post_topic_id, post_time,
    COUNT(post_id) as count
  FROM forum_posts
  WHERE post_topic_id IN (
    SELECT topic_id
    FROM forum_topics
    WHERE topic_forum_id = ' . $forum_id . '
  )
  GROUP BY post_topic_id
  ORDER BY post_time DESC
');
foreach($getPosts as $lastPoster)
{
    $lastPosts[$lastPoster['post_topic_id']] = $lastPoster;
}
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1 に答える 1

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SELECT
   p.post_id, p.post_poster_id, p.post_topic_id, p.post_time, l.count

FROM forum_posts AS p

-- joining with list of latests in a derived table
INNER JOIN

-- getting latest time and count
(SELECT p.post_topic_id, MAX(post_time) AS post_time, COUNT(post_id) AS count
FROM forum_posts AS p
-- filtering forum_id with join, join is usually preferrable than subquery
INNER JOIN forum_topics AS t ON t.topic_id = p.post_topic_id AND t.topic_forum_id = '$forum_id'
GROUP BY post_topic_id)

AS l USING(post_topic_id, post_time)

-- grouping to strip possible post_time-in-one-topic-duplicates
GROUP BY p.post_topic_id
于 2012-06-27T21:21:33.770 に答える