使用 CTE 以逗号分隔的字符串

Question

我有一个字符串 '1,2,3,4,5,6,'，我希望结果像这样的数组：

我已经使用函数尝试过它，也通过将它转换为 xml 来完成。

我有一个问题：

with cte1 (str1,str2) AS
(
SELECT SUBSTRING('1,2,3,4,5,6,',1,1) X,
SUBSTRING('1,2,3,4,5,6,',CHARINDEX(',','1,2,3,4,5,6,,') +1,LEN('1,2,3,4,5,6,')-2) Y
UNION all
SELECT SUBSTRING(str2,1,1) X ,SUBSTRING(str2,CHARINDEX(',',str2)+1,LEN(str2)-2) Y
FROM CTE1
WHERE SUBSTRING(str2,CHARINDEX(',',str2)+0,1) <> ' ' )
SELECT str1 FROM CTE1;

给出了预期的结果。但如果我更改字符串，它会给出随机结果，例如：

with cte1 (str1,str2) AS
(
SELECT SUBSTRING('24,78,45,56,',1,1) X,
SUBSTRING('24,78,45,56,',CHARINDEX(',','24,78,45,56,') +1,LEN('24,78,45,56,')-2) Y
UNION all
SELECT SUBSTRING(str2,1,1) X ,SUBSTRING(str2,CHARINDEX(',',str2)+1,LEN(str2)-2) Y
FROM CTE1
WHERE SUBSTRING(str2,CHARINDEX(',',str2)+0,1) <> ' ' )
SELECT str1 FROM CTE1;

结果：

Answer 1

您可以使用递归 CTE

Declare @list NVARCHAR(MAX) = '1,2,3,4,5'
DECLARE @length INT = LEN(@list) + 1;

   WITH a AS
   (
       SELECT
           [start] = 1,
           [end]   = COALESCE(NULLIF(CHARINDEX(',', 
                       @List, 1), 0), @length),
           [value] = SUBSTRING(@list, 1, 
                     COALESCE(NULLIF(CHARINDEX(',', 
                       @List, 1), 0), @length) - 1)
       UNION ALL
       SELECT
           [start] = CONVERT(INT, [end]) + 1,
           [end]   = COALESCE(NULLIF(CHARINDEX(',', 
                       @list, [end] + 1), 0), @length),
           [value] = SUBSTRING(@list, [end] + 1, 
                     COALESCE(NULLIF(CHARINDEX(',', 
                       @list, [end] + 1), 0), @length)-[end]-1)
       FROM a
       WHERE [end] < @length
   )
    SELECT [value]
   FROM a
   WHERE LEN([value]) > 0
   OPTION (MAXRECURSION 0);

Answer 2

这仅在字符串类似于 '12,34,45,56....' 时有效，即字符串包含两位数字的通信分隔值

with cte1 (str1,str2) AS
(
 SELECT SUBSTRING('24,78,45,56,',1,2) X,
        SUBSTRING('24,78,45,56,',CHARINDEX(',','24,78,45,56,') +1,LEN('24,78,45,56,')-2) Y
 UNION all
 SELECT SUBSTRING(str2,1,2) X ,SUBSTRING(str2,CHARINDEX(',',str2)+1,LEN(str2)-2) Y
 FROM CTE1
 WHERE SUBSTRING(str2,CHARINDEX(',',str2)+0,2) <> ' ' )
 SELECT str1 FROM CTE1;

您应该通过在用户定义函数上创建接受逗号分隔字符串并为此字符串提供 table 值的通用解决方案

像这样的函数定义

CREATE FUNCTION SplitItem( @ItemIDs VARCHAR(MAX))
RETURNS @ItemTable TABLE ( Item VARCHAR(200) )
AS 
BEGIN
    DECLARE @Item VARCHAR(200)
    DECLARE @Index INT

    WHILE LEN(@ItemIDs) <> 0 
        BEGIN
            SET @Index = PATINDEX('%,%', @ItemIDs)
            IF @Index > 0 
                BEGIN
                    SET @Item = SUBSTRING(@ItemIDs, 1, @Index - 1) 
                    SET @ItemIDs = RIGHT(@ItemIDs, LEN(@ItemIDs) - @Index)
                    INSERT  INTO @ItemTable
                    VALUES  ( @Item )
                END
            ELSE 
                BEGIN
                    BREAK
                END
        END
    SET @Item = @ItemIDs 
    INSERT  INTO @ItemTable
    VALUES  ( @Item )

    RETURN
END

并像这样使用这个函数

SELECT Item 
FROM SplitItem('1,2,3,44,55,66,77')

这将给出这样的输出

1 2 3 44 55 66 77

Answer 3

你可以这样做：

DECLARE @string NVARCHAR(MAX) =  '1,2,3,4,5,6,',
        @xml xml

select @xml = cast('<d><q>'+REPLACE(@string,',','</q><q>')+'</q></d>' as xml)

SELECT n.v.value('.','nvarchar(2)')
FROM @xml.nodes('/d/q') AS n(v);

结果：

----
1
2
3
4
5
6


(7 row(s) affected)

使用 CTE 以逗号分隔的字符串

comma separated string using CTE

tsql

sql-server

common-table-expression