Question

好的，所以说我有两张桌子。

问题

questionID
QuestionDescription

回答

AnswerID
QuestionID
AnswerDescription
CreatedDate

并说我想创建一个查询，返回问题和最新创建的答案，如这些列

QuestionID QuestionName AnswerDescription CreatedDate

这可能吗？

我可以进行查询以获取问题和答案的所有组合

SELECT q.QuestionID, q.QuestionName, a.AnswerDescription, a.CreatedDate FROM QUESTION q
INNER JOIN ANSWER a
ON q.questionID = a.QuestionID

但有没有办法我可以做这样的事情，但是它只返回最新答案而不是全部答案？

Answer 1

SELECT q.QuestionID, 
       q.QuestionName, 
       a.AnswerDescription, 
       a.CreatedDate
FROM QUESTION AS q
  INNER JOIN (SELECT QuestionID,
                     AnswerDescription,
                     CreatedDate,
                     ROW_NUMBER() OVER(PARTITION BY QuestionID 
                                       ORDER BY CreatedDate DESC) AS rn
              FROM ANSWER) AS a       
    ON q.questionID = a.QuestionID AND 
       a.rn = 1

Answer 2

获得每个问题，SQL Server 2005 +

SELECT
   q.QuestionID, q.QuestionName,
   a.AnswerDescription, a.CreatedDate
FROM
    QUESTION q
    CROSS APPLY
    (
     SELECT TOP 1 a2.AnswerDescription, a2.CreatedDate
     FROM ANSWER a2
     WHERE q.questionID = a2.QuestionID
     ORDER BY a2.CreatedDate DESC
    ) a

Answer 3

SELECT top 1 q.QuestionID, q.QuestionName, a.AnswerDescription, a.CreatedDate FROM QUESTION q
INNER JOIN ANSWER a
ON q.questionID = a.QuestionID
ORDER BY a.CreatedDate DESC

如何获得链接表的前1名？

3 个答案: