PHP - Join 语句重复记录

Question

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();

然后我做一个 while 循环来显示所有记录:

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

问题是，在 while 循环期间，我有时会得到很好的结果!

它应该看起来像这样:

forum1
forum2
forum3
forum4
forum5
forum6

等等

但有时我会得到这样的结果:

forum1
forum1
forum1
forum1
forum2
forum3
forum4
forum5
forum6

某些行(哪一行是相当随机的)正在“重复”。

有人可以帮我解释一下吗？

Answer 1

尝试通过添加GROUP BY t.forum_id进行分组:

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