Question

我试图通过Threads表中的线程返回最新的5个主题。然后我还需要加入主题表，将topic_name +从线程表连接返回到author表并返回作者名称。

如果某个主题在最近的x帖子中多次出现，我只想要最新（最高）的线程ID信息。

SELECT distinct top 5 Topic_ID, Thread_ID from tblThread ORDER BY Thread_ID DESC

只返回5个最近的主题ID＆＃39;如下

topic_id - Thread_id

852 - 2905

852 - 2904，

850 - 2903，

937 - 2902，

937 - 2901

我想回来 852 - 2905 +其他字段，主题名称，作者姓名

850 - 2903 + ..

937 - 2902 + ...

＆安培;接下来的两个主题id

提前致谢：）

Answer 1

这样的事情应该可以解决问题（尽管你需要在那里使用真正的表和列）：

;WITH CTE AS
(
    SELECT *, ROW_NUMBER() OVER(PARTITION BY Topic_ID ORDER BY Thread_ID DESC) RN
    FROM tblThread 
)
SELECT  A.Topic_ID,
        A.Thread_ID,
        B.Topic_Name,
        C.Author_Name
FROM CTE A
INNER JOIN tblTopic B
    ON A.Topic_ID = B.Topic_ID
INNER JOIN tblAuthor C
    ON A.Author_ID = C.Author_ID
WHERE RN = 1

Answer 2

这不起作用：

select topic, max(thread) as thread from tblThread
group by topic
order by thread desc

在那之后你会做任何你需要的加入。

Answer 3

最终答案：

;WITH CTE AS
(
    SELECT top 10 *, ROW_NUMBER() OVER(PARTITION BY Topic_ID ORDER BY Thread_ID DESC) RN
    FROM tblThread 
    ORDER BY tblThread.Thread_ID DESC
)
SELECT  tblThread.Topic_ID,
        tblThread.Thread_ID,
        tblTopic.Subject,
        tblAuthor.UserName
FROM CTE tblThread
INNER JOIN tblTopic
    ON tblThread.Topic_ID = tblTopic.Topic_ID
INNER JOIN tblAuthor
    ON tblThread.Author_ID = tblAuthor.Author_ID
WHERE RN = 1

选择不同的前5个Topic_ID，来自tblThread的Thread_ID ORDER BY Thread_ID DESC

3 个答案: