Question

我目前正在尝试根据为主题提交的回复数量来获取论坛主题。虽然我已经习惯使用SQL一段时间了，但我对理解SQL如何工作有些新意，尽管我觉得我在正确的轨道上。我目前有这个问题：

SELECT * FROM `topics`
INNER JOIN (
    SELECT COUNT(tid) as countedReplies,`tid`
    FROM `replies`
    GROUP BY `tid`
)
ON topics.id = replies.tid
ORDER by replies.countedReplies DESC

表结构如下所示：

主题

ID        Topic Name
1         Filler Topic Name
2         Exciting Posts about Excellence
3         Random name for example

ID       tid       Post
1        3         Hooray! Wonderful!
2        3         I am a post to topic id 3 as well!
3        1         Topic 1 is better than topic 1.

我的预期结果

我没有得到任何回报，虽然我想得到这样的东西：

1. Random name for example
2. Filler Topic Name
3. Exciting Posts about Excellence

Answer 1

您可以使用左连接而不涉及任何子选择

SELECT t.* FROM `topics` t
LEFT JOIN `replies` r
ON t.id = r.tid
GROUP BY t.id
ORDER by count(r.tid) DESC

DEMO

使用SQL连接来确定帖子的顺序

1 个答案: