在 SQL Server 2005 中将逗号分隔的字符串转换为带有序列号的 XML

Question

我正在使用 SQL Server 2005。我有以下内容：

DECLARE @list NVARCHAR(MAX)
DECLARE @xml XML

SET @list = 'aa,bb,cc,dd,ee'

我想用@list 中的数据填写@xml，格式如下：

<row seq="1" col1="aa" />
<row seq="2" col1="bb" />
<row seq="3" col1="cc" />
<row seq="4" col1="dd" />

我尝试将@list 转换为 XML 字符串，如下所示：

SET @xml = '<row>' + REPLACE(@list, ',', '</row><row>') + '</row>'

然后尝试在@xml.query 方法中寻找可以为行添加序列号的 FLWOR 表达式，但我很不走运，因为 没有 let 子句在 SQL 服务器 2005 中。谁能给我一个hint/workaround？谢谢。

Answer 1

这是使用拆分函数的方法...

DECLARE @list NVARCHAR(MAX)
DECLARE @xml XML

SET @list = 'aa,bb,cc,dd,ee'

;with cteSplit as(
    select * from dbo.DelimitedSplit8K(@list,',')),

cteFinal as(
select 
    '<row seq="' + cast(ItemNumber as varchar(64)) + '"  col1="' + Item + '" />' as Item
from cteSplit)

select Item from cteFinal --for XML AUTO

Here is the function 这已被证明是一种快速拆分字符串的方法：

CREATE FUNCTION [dbo].[DelimitedSplit8K] (@pString VARCHAR(8000), @pDelimiter CHAR(1))
--WARNING!!! DO NOT USE MAX DATA-TYPES HERE!  IT WILL KILL PERFORMANCE!

RETURNS TABLE WITH SCHEMABINDING AS
RETURN

/* "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
enough to cover VARCHAR(8000)*/

  WITH E1(N) AS (
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
                ),                          --10E+1 or 10 rows
       E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
       E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
 cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
                     -- for both a performance gain and prevention of accidental "overruns"
                 SELECT TOP (ISNULL(DATALENGTH(@pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
                ),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                 SELECT 1 UNION ALL
                 SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(@pString,t.N,1) = @pDelimiter
                ),
cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
                 SELECT s.N1,
                        ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1,8000)
                   FROM cteStart s
                )
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
 SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),
        Item       = SUBSTRING(@pString, l.N1, l.L1)
   FROM cteLen l
;
GO

Answer 2

老实说，第一次看scSimon的回答时，我并不喜欢。过去，我在 CROSS JOIN 指数爆炸方面有过一些糟糕的经历（我最终得到了十亿行 table :-)）。因此，我决定使用如下更全面的方法： 1.将逗号分隔列表转换为XML:

的函数

CREATE FUNCTION [dbo].[Delimited2XML](@pList NVARCHAR(MAX), @pDelimiter NCHAR(1))
RETURNS XML
AS
BEGIN
    DECLARE @res NVARCHAR(MAX)    
    DECLARE @LEN INT
    SET @LEN = LEN(@pList)

    SET @res = '<root>'

    IF (@pList IS NOT NULL AND
        @LEN > 0 AND
        @pDelimiter IS NOT NULL AND
        LEN(@pDelimiter) > 0)
    BEGIN
        DECLARE @startIdx INT
        DECLARE @curIdx INT
        SET @startIdx = 1
        SET @curIdx = 1

        DECLARE @i INT
        SET @i = 0

        WHILE @curIdx > 0
        BEGIN
            SET @i = @i + 1;
            SET @curIdx = CHARINDEX(@pDelimiter, @pList, @startIdx /*start_location*/)

            IF (@curIdx > 0)
            BEGIN
                -- create a xml node with this format: <row seq="i" item="item_i" />
                SET @res = @res + ('<row Seq="' + LTRIM(STR(@i)) + '" Item="' + SUBSTRING(@pList, @startIdx /*start*/, @curIdx - @startIdx /*length*/) + '" />')
                SET @startIdx = @curIdx + 1
            END
            ELSE
            BEGIN
                SET @res = @res + ('<row Seq="' + LTRIM(STR(@i)) + '" Item="' + SUBSTRING(@pList, @startIdx /*start*/, @LEN /*length*/) + '" />')
            END
        END

    END

    SET @res = @res + '</root>'
    RETURN CAST(@res AS XML)
END

将XML转换为table的函数：

创建函数 [dbo].[DelimitedSplit](@pString NVARCHAR(MAX), @pDelimiter NCHAR(1)) RETURNS TABLE 作为 RETURN 与数据作为 ( SELECT dbo.Delimited2XML(@pString, @pDelimiter) AS XML数据 ) SELECT Tab.XMLCol.value('@Seq', 'INTEGER') 作为序列, Tab.XMLCol.value('@Item', 'NVARCHAR(MAX)') 作为项目来自 tData 交叉应用 XMLData.nodes('/root/row') AS Tab(XMLCol)

然后我用一个包含 1200 多个项目的字符串测试了这两个函数，DelimitedSplit() 和 DelimitedSplit8K()。 DelimitedSplit() 耗时 240 毫秒完成，而 DelimitedSplit8K() 仅耗时 20 毫秒，仅为 DelimitedSplit() 时间的 8%。因此，DelimitedSplit8K() 具有更好的性能。

在 SQL Server 2005 中将逗号分隔的字符串转换为带有序列号的 XML

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