我有下表:
Code Ref Value
A1 Car A
A1 Car -
A1 Car B
B2 Truck CC
B2 Truck D
B2 Truck -
C3 Van E
C3 Van F
C3 Van -
C3 Van G
我想要实现的目标是一个串联的字符串,将所有值组合在一起,如下所示:
Code Ref Value
A1 Car A-B
B2 Truck CCD-
C3 Van EF-G
我离开了示例here,但无处可去。以下是我提出的建议:
SELECT [Table].[Code]
, [Table].[Ref]
, STUFF((SELECT DISTINCT [Value]
FROM [Table2]
FOR XML PATH ('')),1, 1,'') AS Values
FROM [Table]
LEFT JOIN [Table2] ON
[Table2].[Code] = [Table].[Code]
我哪里错了?有没有更有效的方法来做到这一点?
答案 0 :(得分:3)
您没有将您的内部和外部引用链接到[Table]
,您还需要使外部引用不同。最后,您需要在子查询中没有列名,或者需要[text()]
SELECT [Code]
,[Ref]
,STUFF((SELECT DISTINCT [Value] AS [text()]
FROM [Table] AS T2
WHERE T1.Code = T2.Code -- LINK HERE
AND T2.Ref = T2.Ref -- AND HERE
FOR XML PATH ('')
),1, 1,'') AS [Values]
FROM [Table] AS T1
GROUP BY T1.Code, T1.Ref; -- GROUP BY HERE
顺便说一句,您不需要使用STUFF
,因为您没有分隔符,STUFF
通常用于从字符串的开头删除选定的分隔符。因此,当您有,value1,value2,value3
之类的字符串时,STUFF(string, 1, 1, '')
会将''
的第一个字符替换为value1,value2,value3
。
你还应该使用value
xquery方法来确保你没有被特殊字符绊倒,如果你没有尝试连接">>"
和"<<"
你不会像你想要的那样得到">><<"
,你会得到">><<"
,所以更好的查询是:
SELECT t1.Code,
t1.Ref,
[Values] = (SELECT DISTINCT [text()] = [Value]
FROM [Table] AS t2
WHERE T1.Code = T2.Code
AND T2.Ref = T2.Ref
FOR XML PATH (''), TYPE
).value('.', 'NVARCHAR(MAX)')
FROM [Table] AS T1
GROUP BY t1.Code, t1.Ref;
<强>附录强>
根据对问题的最新修改,好像您的Value
列来自另一个表,并通过Code
链接到第一个表。如果有的话,这会使您的查询更简单。您不需要JOIN
,但仍需要确保有一个表达式将外部表与子查询的内部表链接起来。我假设第一个表中的行是唯一的,因此您可能不需要该组:
SELECT t1.Code,
t1.Ref,
[Values] = (SELECT DISTINCT [text()] = t2.[Value]
FROM [Table2] AS t2
WHERE T1.Code = T2.Code
FOR XML PATH (''), TYPE
).value('.', 'NVARCHAR(MAX)')
FROM [Table] AS T1;
工作示例
CREATE TABLE #Table1 (Code CHAR(2), Ref VARCHAR(10));
INSERT #Table1 VALUES ('A1', 'Car'), ('B2', 'Truck'), ('C3', 'Van');
CREATE TABLE #Table2 (Code CHAR(2), Value VARCHAR(2));
INSERT #Table2
VALUES ('A1', 'A'), ('A1', '-'), ('A1', 'B'),
('B2', 'CC'), ('B2', 'D'), ('B2', '-'),
('C3', 'F'), ('C3', '-'), ('C3', 'G');
SELECT t1.Code,
t1.Ref,
[Values] = (SELECT DISTINCT [text()] = t2.[Value]
FROM #Table2 AS t2
WHERE T1.Code = T2.Code
FOR XML PATH (''), TYPE
).value('.', 'NVARCHAR(MAX)')
FROM #Table1 AS T1;