Question

如果这是重复的话我很抱歉。请指出我正确的问题。我正在使用SQL SERVER 2008.我使用下面的查询，因为我需要从3个表中获取数据。

SELECT qc.FileID as [FileID],    
qc.QID1 as [QID1],    
xqs.SID1 as [SID1],   
xqc.CID1 as [CID1],  
xqs.Comments as [SComments],  
xqc.Comments as [CComments]  
FROM QCTable(nolock) qc  
JOIN QCSectionTable (nolock) xqs ON qc.QCID = xqs.QCID  
LEFT JOIN QCChargeTable (nolock) xqc ON xqc.QCXrefID = xqs.QCXrefID

对于上面我就是这样 FieID1 SID1 SID1 CID1 SComments CComments

我有一行如下

FileID1  QID1 SID1 CID1 SComments  CComments

我需要将上面的行拆分为

FileID1 QID1 SID1 null SComments
FileID1 QID1 SID1 CID1 CComments

提前致谢。

Answer 1

最简单的方法是union all：

select FileID1, QID1, SID1, null as cId1, SComments
from table t
union all
select  FileID1, QID1, SID1, cId1, CComments
from table t;

如果您有大量数据，使用cross apply或cross join执行此操作可能会快一点：

select v.*
from table t cross apply
     (values (FileID1, QID1, SID1, null, SComments),
             (FileID1, QID1, SID1, cId1, CComments)
     ) v(FileID1, QID1, SID1, cId1, CComments);

优点是这只能扫描一次表。

Answer 2

SELECT FileID1, QID1, DID1, null, SComments
FROM table
UNION ALL
SELECT FileID1, QID1, SID1, CID1, CComments
FROM table

Answer 3

你可以使用UNION ALL执行类似的操作：

SELECT 
     qc.FileID AS [FileID1]
    ,qc.QID1 AS [QID1]
    ,xqs.SID1 AS [SID1]
    ,NULL AS [CID1]    --assigning default value as null
    ,xqs.Comments AS [SComments]
FROM QCTable(NOLOCK) qc
JOIN QCSectionTable(NOLOCK) xqs ON qc.QCID = xqs.QCID
LEFT JOIN QCChargeTable(NOLOCK) xqc ON xqc.QCXrefID = xqs.QCXrefID

UNION ALL

SELECT 
     qc.FileID AS [FileID1]
    ,qc.QID1 AS [QID1]
    ,xqs.SID1 AS [SID1]
    ,xqc.CID1 AS [CID1]
    ,xqc.Comments AS [CComments]
FROM QCTable(NOLOCK) qc
JOIN QCSectionTable(NOLOCK) xqs ON qc.QCID = xqs.QCID
LEFT JOIN QCChargeTable(NOLOCK) xqc ON xqc.QCXrefID = xqs.QCXrefID

SQL：根据列将一行拆分为两行

3 个答案: