PHP-Join语句复制记录

我有一个相当大的查询，它基本上向我的用户显示了我存储在数据库中的不同论坛：

    $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();

然后我执行while循环以显示所有记录：

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

问题是，在while循环中，我有时会得到很好的结果

应该是这样的：

forum1
forum2
forum3
forum4
forum5
forum6

forum1
forum1
forum1
forum1
forum2
forum3
forum4
forum5
forum6

等等

但有时我会得到这样的结果：

forum1
forum2
forum3
forum4
forum5
forum6

forum1
forum1
forum1
forum1
forum2
forum3
forum4
forum5
forum6

有些行是非常随机的，哪一行被“复制”

有人能帮我解释一下吗？

尝试通过添加t.forum\u id分组：

---

据推测，查询SELECT t.forum\u id FROM forum\u topics t会产生相同的错误？@草莓你想详细说明一下吗？只是一个猜测，但是。。。我想说的是，你的第三个加入子查询，它会在主查询上带来帖子，这会造成重复，因为你可能在一个论坛上有很多帖子。你能单独运行子查询吗？你把它命名为lp并检查是否有重复的forum\u id字段？只是想确定问题是在PHP还是MySQL中。这个连接看起来很奇怪：从forum\u cats作为t join forum\u cats作为c on c.forum\u id=t.forum\u type\u id。什么是forum\u cats类别？，为什么您需要通过论坛id和类型id来加入该表？它看起来像是一个错误，即使不是，也可能返回重复的。或者将第一次选择更改为“选择不同”。毕竟，如果没有什么可聚合的，你为什么要分组？无论哪种方式，这都将消除症状，但在许多情况下，意外的重复行表示需要解决的错误。现在，您只是在抑制症状。如果确实添加了GROUP BY，则应在ORDER BY之前添加。