sqlserver split函數

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個字符，客戶說選太多項目時會丟失數據，分析函數，直接把nvarchar(4000)改成Text，可以支持更長的字符串，自信滿滿的在客戶機子上運行，居然有異常，跟蹤代碼如果只輸入
1216，‘，’,返回結果是12，艹，輸入‘1216,’,','顯示正常，不應該啊，仔細看代碼有/2部分，猜測可能是nvarchar計算長度問題，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

 使用過程中發現如果超出4000長度的話，split依然會有問題，將

@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