如何加入到列中具有多个值的表？

Question

我有一个人员表,其中包含一个错误代码字段,可以包含多个错误代码(001,002,003 ...).我知道这是一个架构问题,但这是一个供应商应用程序,我无法控制架构,所以我必须使用我所拥有的.

还有一个Error表包含ErrorCode(char(3))和Descript(char(1000)).在我的查询中,Person.ErrorCode连接到Error.ErrorCode以获取相应描述的值.

对于只有一个错误代码的人员记录,我可以毫无问题地获得相应的描述.我想要做的是以某种方式将Descript值连接到存在多个错误的记录.

例如,这是来自Error表的一些示例数据:

ErrorCode     Descript
001           Problem with person file
002           Problem with address file
003           Problem with grade

以下是我的SELECT on Person上出现的列,其中出现了一个错误的JOIN:

Person.RecID   Person.ErrorCode  Error.Descript
12345          001               Problem with person file
12346          003               Problem with grade
12347          002,003

我想要得到的是:

Person.RecID   Person.ErrorCode  Error.Descript
12345          001               Problem with person file
12346          003               Problem with grade
12347          002,003           Problem with address file, Problem with grade

建议赞赏!

Answer 1

您应该看到:"SQL Server 2005及更高版本中的数组和列表,当表值参数不能删除它"时,Erland Sommarskog有很多方法可以在SQL Server中拆分字符串.本文涵盖几乎所有方法的PRO和CON.通常,您需要创建拆分功能.这是分割函数可用于连接行的方式:

SELECT
    * 
    FROM dbo.yourSplitFunction(@Parameter) b
        INNER JOIN YourCodesTable          c ON b.ListValue=c.CodeValue

我更喜欢使用数字表方法在TSQL中拆分字符串,但是有很多方法可以在SQL Server中拆分字符串,请参阅前面的链接,它解释了每个链接的PRO和CON.

要使Numbers Table方法起作用,您需要执行一次性表设置,这将创建一个Numbers包含1到10,000行的表:

SELECT TOP 10000 IDENTITY(int,1,1) AS Number
    INTO Numbers
    FROM sys.objects s1
    CROSS JOIN sys.objects s2
ALTER TABLE Numbers ADD CONSTRAINT PK_Numbers PRIMARY KEY CLUSTERED (Number)

设置Numbers表后,创建此拆分功能:

CREATE FUNCTION [dbo].[FN_ListToTable]
(
     @SplitOn  char(1)      --REQUIRED, the character to split the @List string on
    ,@List     varchar(8000)--REQUIRED, the list to split apart
)
RETURNS TABLE
AS
RETURN 
(

    ----------------
    --SINGLE QUERY-- --this will not return empty rows
    ----------------
    SELECT
        ListValue
        FROM (SELECT
                  LTRIM(RTRIM(SUBSTRING(List2, number+1, CHARINDEX(@SplitOn, List2, number+1)-number - 1))) AS ListValue
                  FROM (
                           SELECT @SplitOn + @List + @SplitOn AS List2
                       ) AS dt
                      INNER JOIN Numbers n ON n.Number < LEN(dt.List2)
                  WHERE SUBSTRING(List2, number, 1) = @SplitOn
             ) dt2
        WHERE ListValue IS NOT NULL AND ListValue!=''

);
GO 

您现在可以轻松地将CSV字符串拆分为表格并加入其中:

DECLARE @ErrorCode table (ErrorCode varchar(20), Description varchar(30))
INSERT @ErrorCode VALUES ('001','Problem with person file')
INSERT @ErrorCode VALUES ('002','Problem with address file')
INSERT @ErrorCode VALUES ('003','Problem with grade')

DECLARE @Person table (RecID int, ErrorCode varchar(20))
INSERT @Person VALUES (12345 ,'001'    )
INSERT @Person VALUES (12346 ,'003'    )
INSERT @Person VALUES (12347 ,'002,003')


SELECT
    p.RecID,c.ListValue,e.Description
    FROM @Person                                        p
        CROSS APPLY dbo.FN_ListToTable(',',p.ErrorCode) c
        INNER JOIN @ErrorCode                           e ON c.ListValue=e.ErrorCode

OUTPUT:

RecID       ListValue     Description              
----------- ------------- -------------------------
12345       001           Problem with person file 
12346       003           Problem with grade       
12347       002           Problem with address file
12347       003           Problem with grade       

(4 row(s) affected)

您可以使用XML技巧将行连接在一起:

SELECT
    t1.RecID,t1.ErrorCode
        ,STUFF(
                   (SELECT
                        ', ' + e.Description
                        FROM @Person                                        p
                            CROSS APPLY dbo.FN_ListToTable(',',p.ErrorCode) c
                            INNER JOIN @ErrorCode                           e ON c.ListValue=e.ErrorCode
                        WHERE t1.RecID=p.RecID
                        ORDER BY p.ErrorCode
                        FOR XML PATH(''), TYPE
                   ).value('.','varchar(max)')
                   ,1,2, ''
              ) AS ChildValues
    FROM @Person t1
    GROUP BY t1.RecID,t1.ErrorCode

OUTPUT:

RecID       ErrorCode            ChildValues
----------- -------------------- -----------------------------------------------
12345       001                  Problem with person file
12346       003                  Problem with grade
12347       002,003              Problem with address file, Problem with grade

(3 row(s) affected)

这将返回与上面相同的结果集,但可能表现更好:

SELECT
    t1.RecID,t1.ErrorCode
        ,STUFF(
                   (SELECT
                        ', ' + e.Description
                        FROM (SELECT ListValue FROM dbo.FN_ListToTable(',',t1.ErrorCode)) c
                            INNER JOIN @ErrorCode e ON c.ListValue=e.ErrorCode
                        ORDER BY c.ListValue
                        FOR XML PATH(''), TYPE
                   ).value('.','varchar(max)')
                   ,1,2, ''
              ) AS ChildValues
    FROM @Person t1
    GROUP BY t1.RecID,t1.ErrorCode