Question

所以我想从“board_b”中选择回复最多的帖子。我的问题是回复实际上在同一个表中。看看这个：

+---+-----------+---------+
|ID | name      | replyto |
+---+-----------+---------+
| 1 | newthread |         |
| 2 | reply     | 1       |
+---+-----------+---------+

（注意：名称列未设置为那些，只是为了演示）如您所见，1是一个新线程，2是回复1。现在我有一个充满了这些的表，并且表中有更多的列（文本，时间戳等等），但总的想法就像上面那样。

我想要实现的是选择所有线程，并按大多数回复排序（并且还限制为0,20）。我已经尝试过加入表格，但这对我来说太复杂了，所以示例代码会很棒。

Answer 1

这样的事情会做到：

SELECT board.id, board.name, COUNT(reply.id)
FROM board_b board INNER JOIN board_b reply ON board.id = reply.replyto
GROUP BY board.id, board.name
ORDER BY COUNT(reply.id) desc
LIMIT 20

Answer 2

您想使用group by：

select replyto as thread, count(*) as cnt
from board_b
group by replyto
order by cnt desc
limit 0, 20;

Answer 3

select c.replyto, c.replycount
from
(
    select a.replyto as replyto, count(*) as replycount
    from board_b a
    inner join (
                select id, name, replyto
                from board_b
                where replyto is null
                ) b
        on b.id = a.replyto
    group by a.replyto
) c
where c.replycount between 0 and 20
order by c.replycount desc

SQL Select加入同一个表（按大多数回复排序）

3 个答案: