Question

需要一些帮助构建我的查询。我想我需要一个子查询，但我不太确定如何在我的上下文中使用它们。我有以下表格和数据，

people
ID, Name
1, David
2, Victoria
3, Brooklyn
4, Tom
5, Katie
6, Suri
7, Kim
8, North
9, Kanye
10,James
11,Grace


relationship
peopleID, Relationship, relatedID
3,Father,1
3,Mother,2
6,Father,4
6,Mother, 5
8,Mother,7
8,Mother,9
11,Father,10

我有以下查询

SELECT DISTINCT p.ID, p.name, f.ID, f.name, m.ID, m.name 
FROM people AS p 
LEFT JOIN relationship AS fr ON p.ID = fr.peopleID 
LEFT JOIN people AS f ON fr.relatedID = f.ID 

LEFT JOIN relationship AS mr ON p.ID = mr.peopleID 
LEFT JOIN people AS m ON mr.relatedID = m.ID 
WHERE p.ID IN(3,6,8,11) 
AND (
     mr.Relationship IN('Mother','Stepmother') 
OR   fr.Relationship IN('Father','Stepfather')
    )

上面的查询输出以下数据

3,Brooklyn,1,David,1,David
3,Brooklyn,1,David,2,Victoria
3,Brooklyn,2,Victoria,2,Victoria
6,Suri,4,Tom,4,Tom
6,Suri,4,Tom,5,Katie
6,Suri,5,Katie,5,Katie
8,North,7,Kim,7,Kim
8,North,9,Kanye,7,Kim
8,North,9,Kanye,9,Kanye
11,Grace,10,James,10,James

我有点理解发生了什么，因此我认为我可能需要一个子查询或者可能需要一个联合来让父母先行，然后再建立这些结果。我想输出以下内容，有人可以帮忙吗？

3,Brooklyn,1,David,2,Victoria
6,Suri,4,Tom,5,Katie
8,North,9,Kanye,7,Kim
11,Grace,10,James,, <-should display no mother details (same for the father if father was not in the data)

Answer 1

抱歉，我现在无法查询查询。这有用吗？

SELECT DISTINCT p.ID, p.name, f.ID, f.name, m.ID, m.name 
FROM people AS p 
LEFT JOIN relationship AS fr 
       ON p.ID = fr.peopleID
      AND fr.relationship IN ('Father','Stepfather')
LEFT JOIN people AS f
       ON fr.relatedID = f.ID
LEFT JOIN relationship AS mr
       ON p.ID = mr.peopleID
      AND mr.relationship IN('Mother','Stepmother')
LEFT JOIN people AS m 
       ON mr.relatedID = m.ID 
WHERE p.ID IN(3,6,8,11)

关键是要与LEFT JOIN一起摆脱使用（WHERE A OR B）。它给结果的逻辑带来了太多的不确定性

Answer 2

这就是你想要的吗？

SELECT p.ID, p.Name, p1.ID, p1.Name
FROM relationship r
    INNER JOIN people p ON p.ID = r.peopleID
    INNER JOIN people p1 ON p1.ID = r.relatedID

select cast（p.id as nvarchar（max））+'，'+ p.name +（SELECT cast（p1.id as varchar（max））+'，'+ p1.name FROM relationship r1 inner join r1.relatedID = p1.ID上的人p1，其中r1.peopleID = p.id表示xml路径（''））来自关系r内部联接人p p.ID = r.peopleID group by p.ID，p.name

如果您需要更多信息，请与我们联系。

Answer 3

即使您已经接受了答案，但我仍然想提供我的答案：

WITH familly AS
(
    SELECT
         child.ID AS childID
        ,child.Name AS childName
        ,Relationship AS relationship
        ,parent.ID AS parentID
        ,parent.Name AS parentName
    FROM relationship
    LEFT JOIN people AS child ON child.ID = peopleID
    LEFT JOIN people AS parent ON parent.ID = relatedID
)
SELECT
     t.childID
    ,t.childName
    ,STUFF(ISNULL((
        SELECT ', ' + CAST(x.parentID AS NVARCHAR(10)) + ', ' + x.parentName
        FROM familly x
        WHERE x.childID = t.childID
        GROUP BY x.parentID, x.parentName
        FOR XML PATH (''), TYPE
    ).value('.','VARCHAR(max)'), ''), 1, 2, '') [Parents]
FROM familly t
WHERE t.childID IN(3,6,8,11) 
GROUP BY t.childID, t.childName

不再LEFT JOIN，而且更具可读性。你应该开始联合使用表relationship，所以：

一方面，您可以作为孩子加入people
另一方面，您可以作为父母联合people。

然后，我使用了WITH语句来提供更好的可读性。最后， operation STUFF (Transact-SQL)将多个字符串（父项）连接成一行。

参考文献：

我的查询输出不太正确，可能是子查询？

3 个答案: