T-SQL: Opposite to string concatenation - how to split string into multiple records [duplicate]

Answer 1

Here's a Split function that is compatible with SQL Server versions prior to 2005.

CREATE FUNCTION dbo.Split(@data nvarchar(4000), @delimiter nvarchar(100))  
RETURNS @result table (Id int identity(1,1), Data nvarchar(4000)) 
AS  
BEGIN 
    DECLARE @pos   INT
    DECLARE @start INT
    DECLARE @len   INT
    DECLARE @end   INT

    SET @len   = LEN('.' + @delimiter + '.') - 2
    SET @end   = LEN(@data) + 1
    SET @start = 1
    SET @pos   = 0

    WHILE (@pos < @end)
    BEGIN
        SET @pos = CHARINDEX(@delimiter, @data, @start)
        IF (@pos = 0) SET @pos = @end

        INSERT @result (data) SELECT SUBSTRING(@data, @start, @pos - @start)
        SET @start = @pos + @len
    END

    RETURN
END

Answer 2

Using CLR, here's a much simpler alternative that works in all cases, yet 40% faster than the accepted answer:

using System;
using System.Collections;
using System.Data.SqlTypes;
using System.Text.RegularExpressions;
using Microsoft.SqlServer.Server;

public class UDF
{
    [SqlFunction(FillRowMethodName="FillRow")]
    public static IEnumerable RegexSplit(SqlString s, SqlString delimiter)
    {
        return Regex.Split(s.Value, delimiter.Value);
    }

    public static void FillRow(object row, out SqlString str)
    {
        str = new SqlString((string) row);
    }
}

Of course, it is still 8 times slower than PostgreSQL's regexp_split_to_table.

Answer 3

Slight modification of the solution above so it works with variable-length delimiters.

create FUNCTION dbo.fn_Split2 (@sep nvarchar(10), @s nvarchar(4000))
RETURNS table
AS
RETURN (
    WITH Pieces(pn, start, stop) AS (
      SELECT 1, 1, CHARINDEX(@sep, @s)
      UNION ALL
      SELECT pn + 1, stop + (datalength(@sep)/2), CHARINDEX(@sep, @s, stop + (datalength(@sep)/2))
      FROM Pieces
      WHERE stop > 0
    )
    SELECT pn,
      SUBSTRING(@s, start, CASE WHEN stop > 0 THEN stop-start ELSE 4000 END) AS s
    FROM Pieces
  )

NB: I've used datalength() since len() reports incorrectly if there are trailing spaces.

Answer 4

SELECT substring(commaSeparatedTags,0,charindex(',',commaSeparatedTags))

will give you the first tag. You can proceed similarly to get the second one and so on by combining substring and charindex one layer deeper each time. That's an immediate solution but it works only with very few tags as the query grows very quickly in size and becomes unreadable. Move on to functions then, as outlined in other, more sophisticated answers to this post.

Answer 5

I up-voted "Nathan Wheeler" answer as I found "Cade Roux" answer did not work above a certain string size.

Couple of points

-I found adding the DISTINCT keyword improved performance for me.

-Nathan's answer only works if your identifiers are 5 characters or less, of course you can adjust that...If the items you are splitting are INT identifiers as I am you can us same as me below:

CREATE FUNCTION [dbo].Split
(
    @sep VARCHAR(32), 
    @s VARCHAR(MAX)
)
RETURNS 
    @result TABLE (
        Id INT NULL
    )   
AS
BEGIN
    DECLARE @xml XML
    SET @XML = N'<root><r>' + REPLACE(@s, @sep, '</r><r>') + '</r></root>'

    INSERT INTO @result(Id)
    SELECT DISTINCT r.value('.','int') as Item
    FROM @xml.nodes('//root//r') AS RECORDS(r)

    RETURN
END

Answer 6

I wrote this awhile back. It assumes the delimiter is a comma and that the individual values aren't bigger than 127 characters. It could be modified pretty easily.

It has the benefit of not being limited to 4,000 characters.

Good luck!

ALTER Function [dbo].[SplitStr] ( 
        @txt text 
) 
Returns @tmp Table 
        ( 
                value varchar(127)
        ) 
as 
BEGIN 
        declare @str varchar(8000) 
                , @Beg int 
                , @last int 
                , @size int 

        set @size=datalength(@txt) 
        set @Beg=1 


        set @str=substring(@txt,@Beg,8000) 
        IF len(@str)<8000 set @Beg=@size 
        ELSE BEGIN 
                set @last=charindex(',', reverse(@str)) 
                set @str=substring(@txt,@Beg,8000-@last) 
                set @Beg=@Beg+8000-@last+1 
        END 

        declare @workingString varchar(25) 
                , @stringindex int 



        while @Beg<=@size Begin 
                WHILE LEN(@str) > 0 BEGIN 
                        SELECT @StringIndex = CHARINDEX(',', @str) 

                        SELECT 
                                @workingString = CASE 
                                        WHEN @StringIndex > 0 THEN SUBSTRING(@str, 1, @StringIndex-1) 
                                        ELSE @str 
                                END 

                        INSERT INTO 
                                @tmp(value)
                        VALUES 
                                (cast(rtrim(ltrim(@workingString)) as varchar(127)))
                        SELECT @str = CASE 
                                WHEN CHARINDEX(',', @str) > 0 THEN SUBSTRING(@str, @StringIndex+1, LEN(@str)) 
                                ELSE '' 
                        END 
                END 
                set @str=substring(@txt,@Beg,8000) 

                if @Beg=@size set @Beg=@Beg+1 
                else IF len(@str)<8000 set @Beg=@size 
                ELSE BEGIN 
                        set @last=charindex(',', reverse(@str)) 
                        set @str=substring(@txt,@Beg,8000-@last) 
                        set @Beg=@Beg+8000-@last+1 

                END 
        END     

        return
END