(SQL) 单行查询结果

Question

所以我有两个表，分别命名为“问题”和“答案”

我为这两个表做了一个 INNER JOIN

SELECT Questions.ID, Questions.QText, Answers.AText
FROM Questions INNER JOIN Answers
ON Questions.ID=Answers.QuestionID;

结果如下所示： 但是，您可以清楚地看到，该问题每次显示 4 次，其中一个答案。

现在我的问题是：是否可以将结果放在一行中，由

组成

[ID] - [问题] - [Answer1] - [Answer2] - [Answer3] - [Answer4]

Answer 1

对 CSV 使用 CROSS APPLY。不要内联，那么你需要一个分组......

SELECT q.ID, q.QText, Answers = STUFF(x.csv, 1, 1, '')
FROM Questions q
CROSS APPLY
    (
    SELECT
        '-' + a.Atext
    FROM
        Answers a
    WHERE
        a.QuestionID = q.ID
    FOR XML PATH ('')
    ) x (csv)

Answer 2

您可以将此查询用于枢轴：

SELECT QID, QText, [1], [2], [3], [4]
FROM (SELECT Q.ID AS QID, A.ID AS AID, Q.QText, A.AText FROM Questions AS Q 
INNER JOIN Answers AS A ON Q.ID = A.QuestionID) QA
PIVOT
(
    MAX(AText)
    FOR AID
    IN ([1], [2], [3], [4])
) AS PV

但是：您必须为答案表使用组合主键。 使用此数据透视表，答案 ID 每次都必须为 1、2、3、4。否则你得不到你的答案。 FOR AID 声明，使用哪一列。 否则，您可以在名为“AnswerNr”或类似名称的答案中添加一列。在此列中，您将 1 到 4 作为答案并将查询更改为：

SELECT QID, QText, [1], [2], [3], [4]
FROM (SELECT Q.ID AS QID, ->A.AnswerNr<-, Q.QText, A.AText FROM Questions AS Q 
INNER JOIN Answers AS A ON Q.ID = A.QuestionID) QA
PIVOT
(
    MAX(AText)
    FOR ->AnswerNr<-
    IN ([1], [2], [3], [4])
) AS PV

Answer 3

要在单行上获得所有答案的问题，请使用COALESCE：

DECLARE @Answer VARCHAR(8000) 
SELECT Questions.ID, Questions.QText, @Answer = COALESCE(@Answer + ', ', '') + AText
FROM Questions INNER JOIN Answers ON Questions.ID=Answers.QuestionID
WHERE AText IS NOT NULL

如果您使用的是 SQL Server 2005，则可以使用 FOR XML PATH 命令。

SELECT Questions.ID, Questions.QText,
       (STUFF((SELECT CAST(', ' + [AText] AS VARCHAR(MAX)) 
               FROM Answers 
               WHERE Questions.ID = Answers.QuestionID
         FOR XML PATH ('')), 1, 2, '')) AS Answers
 FROM Questions