PHP - 加入语句复制记录

Question

我有相当大的查询，这基本上显示了不同的论坛我已经保存在我的数据库，我的用户：

$stmt = $dbh->prepare(" 
    SELECT 
     c.forum_id as category_id, 
     c.forum_name as category_name, 
     t.forum_id as id, 
     t.forum_name as name, 
     t.forum_desc as description, 
     (SELECT COUNT(*) FROM forum_topics WHERE forum_id=t.forum_id AND topic_deleted=0) as topics_count, 
     (SELECT COUNT(*) FROM forum_posts WHERE forum_id=t.forum_id AND post_deleted=0) as posts_count, 
     (SELECT COUNT(*) FROM forum_posts WHERE topic_id=lp.topic_id AND post_deleted=0) as last_post_count, 
     lp.topic_id as last_post_topic_id, 
     lp.topic_title as last_post_topic_title, 
     lp.post_time as last_post_time, 
     lp.username as last_post_username 
    FROM forum_cats as t 
    JOIN forum_cats as c on c.forum_id = t.forum_type_id 
    left join (
     SELECT 
      ft.topic_id, 
      ft.title as topic_title, 
      tmp.post_time, 
      u.username, 
      fp.forum_id 
     FROM 
      forum_posts fp 
      join forum_topics ft on ft.topic_id = fp.topic_id 
      join users u on u.id = fp.userid 
      join (
       select forum_id, max(`post_time`) `post_time` 
       from forum_posts fp 
       where fp.post_deleted = 0 
       group by forum_id 
       ) as tmp on (fp.forum_id = tmp.forum_id and fp.post_time = tmp.post_time) 
     where post_deleted = 0 and ft.topic_deleted = 0 
    ) as lp on lp.forum_id = t.forum_id 
    where t.forum_active = 1 and c.forum_active = 1 
    order by category_id, t.forum_id 
"); 

    $stmt->execute(); 

我然后做一个while循环来显示所有的记录：

while (($row = $stmt->fetch())) { 
echo $row['name']; 
} 

的问题是，while循环过程中，我获得优秀成果有时！

它应该是这样的：

forum1 
forum2 
forum3 
forum4 
forum5 
forum6 

等

但有时我得到的结果是这样的：

forum1 
forum1 
forum1 
forum1 
forum2 
forum3 
forum4 
forum5 
forum6 

某些行（这是相当随机哪一行）是被“重复”。

有人能帮我解释一下吗？

Answer 1

，尝试按加入GROUP BY t.forum_id：

SELECT 
    c.forum_id as category_id, 
    c.forum_name as category_name, 
    t.forum_id as id, 
    t.forum_name as name, 
    t.forum_desc as description, 
    (SELECT COUNT(*) FROM forum_topics WHERE forum_id=t.forum_id AND topic_deleted=0) as topics_count, 
    (SELECT COUNT(*) FROM forum_posts WHERE forum_id=t.forum_id AND post_deleted=0) as posts_count, 
    (SELECT COUNT(*) FROM forum_posts WHERE topic_id=lp.topic_id AND post_deleted=0) as last_post_count, 
    lp.topic_id as last_post_topic_id, 
    lp.topic_title as last_post_topic_title, 
    lp.post_time as last_post_time, 
    lp.username as last_post_username 
FROM forum_cats as t 
JOIN forum_cats as c on c.forum_id = t.forum_type_id 
left join (
    SELECT 
     ft.topic_id, 
     ft.title as topic_title, 
     tmp.post_time, 
     u.username, 
     fp.forum_id 
    FROM 
     forum_posts fp 
     join forum_topics ft on ft.topic_id = fp.topic_id 
     join users u on u.id = fp.userid 
     join (
      select forum_id, max(`post_time`) `post_time` 
      from forum_posts fp 
      where fp.post_deleted = 0 
      group by forum_id 
      ) as tmp on (fp.forum_id = tmp.forum_id and fp.post_time = tmp.post_time) 
    where post_deleted = 0 and ft.topic_deleted = 0 
) as lp on lp.forum_id = t.forum_id 
where t.forum_active = 1 and c.forum_active = 1 
GROUP BY t.forum_id 
order by category_id, t.forum_id