sqlserver split函数

create FUNCTION [dnt_split]
(
 @splitstring NVARCHAR(4000),
 @separator CHAR(1) = ','
)
RETURNS @splitstringstable TABLE
(
 [item] NVARCHAR(200)
)
AS
BEGIN
    DECLARE @currentindex INT
    DECLARE @nextindex INT
    DECLARE @returntext NVARCHAR(200)
    SELECT @currentindex=1
    WHILE(@currentindex<=datalength(@splitstring)/2)
    BEGIN
        SELECT @nextindex=charindex(@separator,@splitstring,@currentindex)
        IF(@nextindex=0 OR @nextindex IS NULL)
            SELECT @nextindex=datalength(@splitstring)/2+1
        
        SELECT @returntext=substring(@splitstring,@currentindex,@nextindex-@currentindex)
        INSERT INTO @splitstringstable([item])
        VALUES(@returntext)
        
        SELECT @currentindex=@nextindex+1
    END
    RETURN
END

上面版本，最多支持4000个字符，客户说选太多项目时会丢失数据，分析函数，直接把nvarchar(4000)改成Text，可以支持更长的字符串，自信满满的在客户机子上运行，居然有异常，跟踪代码如果只输入
1216，‘，’,返回结果是12，艹，输入‘1216,’,','显示正常，不应该啊，仔细看代码有/2部分，猜测可能是nvarchar计算长度问题，去掉除以/2,如下所示，正常。

ALTER FUNCTION [dbo].[dnt_split]
(
 @splitstring TEXT,
 @separator CHAR(1) = ','
)
RETURNS @splitstringstable TABLE
(
 [item] VARCHAR(200)
)
AS
BEGIN
    DECLARE @currentindex INT
    DECLARE @nextindex INT
    DECLARE @returntext VARCHAR(200)

    SELECT @currentindex=1

    WHILE(@currentindex<=datalength(@splitstring))
    BEGIN
        SELECT @nextindex=charindex(@separator,@splitstring,@currentindex)
        IF(@nextindex=0 OR @nextindex IS NULL)
            SELECT @nextindex=datalength(@splitstring)+1
        
        SELECT @returntext=substring(@splitstring,@currentindex,@nextindex-@currentindex)

        INSERT INTO @splitstringstable([item])
        VALUES(@returntext)
        
        SELECT @currentindex=@nextindex+1
    END
    RETURN
END

 使用过程中发现如果超出4000长度的话，split依然会有问题，将

@splitstring TEXT改成

@splitstring varchar(max)正常

ALTER FUNCTION [dbo].[dnt_split]
(
 @splitstring varchar(max),
 @separator CHAR(1) = ','
)
RETURNS @splitstringstable TABLE
(
 [item] VARCHAR(200)
)
AS
BEGIN
    DECLARE @currentindex INT
    DECLARE @nextindex INT
    DECLARE @returntext VARCHAR(200)

    SELECT @currentindex=1

    WHILE(@currentindex<=datalength(@splitstring))
    BEGIN
        SELECT @nextindex=charindex(@separator,@splitstring,@currentindex)
        IF(@nextindex=0 OR @nextindex IS NULL)
            SELECT @nextindex=datalength(@splitstring)+1
        
        SELECT @returntext=substring(@splitstring,@currentindex,@nextindex-@currentindex)

        INSERT INTO @splitstringstable([item])
        VALUES(@returntext)
        
        SELECT @currentindex=@nextindex+1
    END
    RETURN
END