子查询 - 如何引用外部查询的值

Question

下面的查询正常工作：

SELECT 
   tblCase.ID AS CaseID, tblCase.UserID AS MyCasesFilter, 
   tblGroupMembership.UserID AS GroupShareFilter, 
   tblDirectCaseSharing.ReceiverUserID AS DirectShareFilter, tblCase.EntryDate, 
   tblUser.LastName AS CaseAuthor, tblCase.Name AS CaseName, 
   COUNT(DISTINCT tblCaseImage.ID) AS TotalImages, 
   tblCaseType.Name AS CaseType, tblCase.SiteName, tblCase.Category, 
   tblCase.FollowUpDateTime, tblCase.Notes
FROM     
   tblDirectCaseSharing 
RIGHT OUTER JOIN
   tblCase 
INNER JOIN tblUser ON tblCase.UserID = tblUser.ID ON tblDirectCaseSharing.CaseID = tblCase.ID 
LEFT OUTER JOIN
   tblGroupMembership 
INNER JOIN
   tblGroupCase ON tblGroupMembership.GroupID = tblGroupCase.GroupID ON tblCase.ID = tblGroupCase.CaseID 
LEFT OUTER JOIN
   tblCaseType ON tblCase.CaseTypeID = tblCaseType.ID 
LEFT OUTER JOIN
   tblCaseImage ON tblCase.ID = tblCaseImage.CaseID
GROUP BY 
   tblCase.ID, tblCaseType.Name, tblCase.SiteName, tblCase.EntryDate, 
   tblCase.Category, tblCase.FollowUpDateTime, tblCase.Notes, tblCase.UserID, 
   tblGroupMembership.UserID, tblDirectCaseSharing.ReceiverUserID, 
   tblUser.LastName, tblCase.Name
HAVING 
   (tblCase.UserID = 1) 
   AND (tblGroupMembership.UserID = 2) 
   AND (tblDirectCaseSharing.ReceiverUserID = 3)
ORDER BY 
   tblCase.EntryDate DESC

我想使用一个select子查询向上面的结果中添加一个额外的select列，如下：

STUFF((
SELECT ', ' +tblGroup.Name  as [text()] 
FROM     tblCase INNER JOIN
                  tblGroupCase ON tblCase.ID = tblGroupCase.CaseID INNER JOIN
                  tblGroup ON tblGroupCase.GroupID = tblGroup.ID
WHERE tblCase.ID = ***
FOR XML PATH('')
),1,2,'')
AS ConcatGroupShares

子查询有一个子句，我需要获取结果集的第一列。我该如何在子查询中引用那个值呢？

- user2492038

Answer 1

在主查询中加入别名。

SELECT 
   tcase.ID AS CaseID, tblCase.UserID AS MyCasesFilter, 
   tblGroupMembership.UserID AS GroupShareFilter, 
   tblDirectCaseSharing.ReceiverUserID AS DirectShareFilter, tblCase.EntryDate, 
   tblUser.LastName AS CaseAuthor, tblCase.Name AS CaseName, 
   COUNT(DISTINCT tblCaseImage.ID) AS TotalImages, 
   tblCaseType.Name AS CaseType, tblCase.SiteName, tblCase.Category, 
   tblCase.FollowUpDateTime, tblCase.Notes
 FROM     
   tblDirectCaseSharing 
 RIGHT OUTER JOIN
   tblCase As tcase                       <=====

在子查询中使用此别名：

 STUFF((
SELECT ', ' +tblGroup.Name  as [text()] 
FROM     tblCase INNER JOIN
                  tblGroupCase ON tblCase.ID = tblGroupCase.CaseID INNER JOIN
                  tblGroup ON tblGroupCase.GroupID = tblGroup.ID
 WHERE tblCase.ID = tcase.id
 FOR XML PATH('')
 ),1,2,'')
 AS ConcatGroupShares

关于相关子查询的更多信息：

http://en.wikipedia.org/wiki/Correlated_subquery

- cosmos

---

在主查询中使用别名，养成通常使用短（但可能有意义）的表别名的习惯。 :) - Andriy M