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SQL User Defined Function to Parse a Delimited String

, 5 Apr 2016 CPOL
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SQL Function to parse a delimited string and return it as a table. Handles multi-character delimiters and returns the results as a table.

Introduction

Updated!

I've not paid much attention to this since I posted it years ago, but based on a couple requests that came through, and new features available in SQL Server, I thought it deserved a quick refresh.

Particularly, a test for Date values and a DATETIME column have been added. Also a version that uses the XML functions in SQL server to parse the string has been added. The XML approach is more efficient and scales better.

Cheers!

Clayton

 

One of the challenges that always comes up when dealing with data captured from web sites is parsing multi-value fields. Many web forms have "check all that apply" checkbox forms, and the data from questions of this type is often logged as a single delimited field value. 

For example, the index values from a block of check boxes may be logged to a text file or returned to the database as a string of delimited numbers: '1|3|6|11'

The challenge is to take these delimited values and get them into a format that is meaningful to a database user.  The single field of delimited values has to be broken apart and stored as individual rows in a child table related to the source row in the parent table.

The best way to accomplish this is up front in the web application. If this is not an option then it has to be handled when importing to the database. This SQL Server function gives you a quick way to turn the data trapped in delimited strings into meaningful data.

One of the more intriguing capabilities of SQL Server User Defined Functions (UDF) is the ability to return a table as a result. This UDF uses this feature to return each element in the delimited string as a row in a result table. The result from the function can be used like any other table. It can be included in a multi-table query, or returned directly by the function call.

Code

CREATE FUNCTION [fn_ParseText2Table]
  (@p_SourceText VARCHAR(MAX)
  ,@p_Delimeter VARCHAR(100)=',' --default to comma delimited.
  )
 RETURNS @retTable
  TABLE([Position] INT IDENTITY(1,1)
   ,[Int_Value] INT
   ,[Num_Value] NUMERIC(18,3)
   ,[Txt_Value] VARCHAR(MAX)
   ,[Date_value] DATETIME
   )
AS
/*
********************************************************************************
Purpose: Parse values from a delimited string
  & return the result as an indexed table
Copyright 1996, 1997, 2000, 2003 Clayton Groom (<A href="mailto:Clayton_Groom@hotmail.com">Clayton_Groom@hotmail.com</A>)
Posted to the public domain Aug, 2004
2003-06-17 Rewritten as SQL 2000 function.
 Reworked to allow for delimiters > 1 character in length
 and to convert Text values to numbers
2016-04-05 Added logic for date values based on "new" ISDATE() function, Updated to use XML approach, which is more efficient.
********************************************************************************
*/


BEGIN
 DECLARE @w_xml xml;
 SET @w_xml = N'<root><i>' + replace(@p_SourceText, @p_Delimeter,'</i><i>') + '</i></root>';


 INSERT INTO @retTable
     ([Int_Value]
    , [Num_Value]
    , [Txt_Value]
    , [Date_value]
     )
     SELECT CASE
       WHEN ISNUMERIC([i].value('.', 'VARCHAR(MAX)')) = 1
       THEN CAST(CAST([i].value('.', 'VARCHAR(MAX)') AS NUMERIC) AS INT)
      END AS [Int_Value]
    , CASE
       WHEN ISNUMERIC([i].value('.', 'VARCHAR(MAX)')) = 1
       THEN CAST([i].value('.', 'VARCHAR(MAX)') AS NUMERIC(18, 3))
      END AS [Num_Value]
    , [i].value('.', 'VARCHAR(MAX)') AS [txt_Value]
    , CASE
       WHEN ISDATE([i].value('.', 'VARCHAR(MAX)')) = 1
       THEN CAST([i].value('.', 'VARCHAR(MAX)') AS DATETIME)
      END AS [Num_Value]
     FROM @w_xml.nodes('//root/i') AS [Items]([i]);
 RETURN;
END;
GO


--Old version, with some updates...
CREATE FUNCTION [fn_ParseText2Table_old]
 (
 @p_SourceText VARCHAR(MAX)
 , @p_Delimeter  VARCHAR(100) = ',' --default to comma delimited.
 )
RETURNS @retTable TABLE
      (
      [Position]   INT IDENTITY(1, 1)
       , [Int_Value]  INT
       , [Num_Value]  NUMERIC(18, 3)
       , [Txt_Value]  VARCHAR(MAX)
       , [Date_value] DATETIME
      )
AS


/*
********************************************************************************
Purpose: Parse values from a delimited string
  & return the result as an indexed table
Copyright 1996, 1997, 2000, 2003 Clayton Groom (<A href="mailto:Clayton_Groom@hotmail.com">Clayton_Groom@hotmail.com</A>)
Posted to the public domain Aug, 2004
2003-06-17 Rewritten as SQL 2000 function.
 Reworked to allow for delimiters > 1 character in length
 and to convert Text values to numbers
2016-04-05 Added logic for date values based on "new" ISDATE() function
********************************************************************************
*/


  BEGIN
   DECLARE @w_Continue      INT
      , @w_StartPos      INT
      , @w_Length        INT
      , @w_Delimeter_pos INT
      , @w_tmp_int       INT
      , @w_tmp_num       NUMERIC(18, 3)
      , @w_tmp_txt       VARCHAR(MAX)
      , @w_date          DATETIME
      , @w_Delimeter_Len TINYINT;
   IF LEN(@p_SourceText) = 0
    BEGIN
     SET @w_Continue = 0; -- force early exit
    END;
   ELSE
    BEGIN
     -- parse the original @p_SourceText array into a temp table
     SET @w_Continue = 1;
     SET @w_StartPos = 1;
     SET @p_SourceText = RTRIM(LTRIM(@p_SourceText));
     SET @w_Length = DATALENGTH(RTRIM(LTRIM(@p_SourceText)));
     SET @w_Delimeter_Len = LEN(@p_Delimeter);
    END;
   WHILE @w_Continue = 1
    BEGIN
     SET @w_Delimeter_pos = CHARINDEX(@p_Delimeter, (SUBSTRING(@p_SourceText, @w_StartPos, ((@w_Length-@w_StartPos)+@w_Delimeter_Len))));
     IF @w_Delimeter_pos > 0  -- delimeter(s) found, get the value
      BEGIN
       SET @w_tmp_txt = LTRIM(RTRIM(SUBSTRING(@p_SourceText, @w_StartPos, (@w_Delimeter_pos-1))));
       IF ISNUMERIC(@w_tmp_txt) = 1
        BEGIN
         SET @w_tmp_int = CAST(CAST(@w_tmp_txt AS NUMERIC) AS INT);
         SET @w_tmp_num = CAST(@w_tmp_txt AS NUMERIC(18, 3));
        END;
       ELSE
        BEGIN
         SET @w_tmp_int = NULL;
         SET @w_tmp_num = NULL;
        END;
       IF ISDATE(@w_tmp_txt) = 1
        BEGIN
         SET @w_date = CAST(@w_tmp_txt AS DATETIME);
        END;
       ELSE
        BEGIN
         SET @w_date = NULL;
        END;
       SET @w_StartPos = @w_Delimeter_pos + @w_StartPos + (@w_Delimeter_Len - 1);
      END;
     ELSE -- No more delimeters, get last value
      BEGIN
       SET @w_tmp_txt = LTRIM(RTRIM(SUBSTRING(@p_SourceText, @w_StartPos, ((@w_Length-@w_StartPos)+@w_Delimeter_Len))));
       IF ISNUMERIC(@w_tmp_txt) = 1
        BEGIN
         SET @w_tmp_int = CAST(CAST(@w_tmp_txt AS NUMERIC) AS INT);
         SET @w_tmp_num = CAST(@w_tmp_txt AS NUMERIC(18, 3));
        END;
       ELSE
        BEGIN
         SET @w_tmp_int = NULL;
         SET @w_tmp_num = NULL;
        END;
       IF ISDATE(@w_tmp_txt) = 1
        BEGIN
         SET @w_date = CAST(@w_tmp_txt AS DATETIME);
        END;
       ELSE
        BEGIN
         SET @w_date = NULL;
        END;
       SELECT @w_Continue = 0;
      END;
     INSERT INTO @retTable
     VALUES
      (@w_tmp_int
        , @w_tmp_num
        , @w_tmp_txt
        , @w_date
      );
    END;
   RETURN;
  END;
GO

Usage Examples:

Single Character Delimiter

select * from dbo.fn_ParseText2Table('100|120|130.56|Yes|Cobalt Blue|2016-04-04|2000-06-17','|')
/*
Position    Int_Value   Num_value            txt_value   Date_value
----------- ----------- -------------------- ----------- -----------------------
1           100         100.000              100
2           120         120.000              120
3           131         130.560              130.56
4           NULL        NULL                 Yes
5           NULL        NULL                 Cobalt Blue
6           NULL        NULL                 NULL	 2016-04-04 00:00:00.000
7           NULL        NULL                 NULL	 2000-06-17 00:00:00.000


*/

Multi-Character Delimiter

select * from dbo.fn_ParseText2Table('Red, White, and, Blue',', ')
/*
Position    Int_Value   Num_value            txt_value  Date_value
----------- ----------- -------------------- ---------- ----------
1           NULL        NULL                 Red	NULL	
2           NULL        NULL                 White	NULL
3           NULL        NULL                 and	NULL
4           NULL        NULL                 Blue 	NULL
*/ 

Big Multi-Character Delimiter

select * from dbo.fn_ParseText2Table('Red<Tagname>White<Tagname>Blue','<Tagname>')
/* 
Position    Int_Value   Num_value            txt_value  Date_value
----------- ----------- -------------------- ---------- ----------
1           NULL        NULL                 Red	NULL
2           NULL        NULL                 White	NULL
3           NULL        NULL                 and	NULL
4           NULL        NULL                 Blue 	NULL
*/ 

Unfortunately, the only way to use this to process multiple rows is using a cursor.

Here is an example of what the code inside the cursor block would look like to insert parsed values from a string as rows in a child table

As a table in an insert statement:

create table #tmp_Child (parent_id int, ColorSelection varchar(30), SelOrder tinyint)
declare @parent_id int
 ,@ColorSelections varchar(255)
 ,@delim varchar(100) 
set @parent_id = 122
set @ColorSelections = 'Red, White, and, Blue'
set @delim = ', ' 


-- cursor block starts here
insert #tmp_Child (parent_id, ColorSelection, SelOrder)
select @parent_id
 ,t.txt_value
 ,t.position
from dbo.fn_ParseText2Table(@ColorSelections, @delim) as t 
-- cursor block ends here
select * from #tmp_child 
drop table #tmp_child

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

SQLMonger
Web Developer Clayton Groom, LLC
United States United States
I am a database design consultant with over 20 years experience in consulting.

My primary focus is designing and bulding data driven, highly automated OLTP and datatwarehouse applications that leverage the Microsoft SQL Server platform. I am skilled in SQL Server Analysis Services (MDS and Tabular), MDX, DAX, and all the related technologies. I am experienced with SharePoint Business Intelligence and dashboard capabilities, including installation, configuration, and Kerberos authentication set up.

I have worked with SQL Server since version 4.12 and have experience with Oracle, Sybase, Teradata and DB/2 as well.

I would term myself as a Data Warehouse Architect and programmer DBA, with a good dose of system architect and troubleshooter thrown in.

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Comments and Discussions

 
Generalhandling space better. and symbols. Pin
roger_279-Sep-10 13:11
memberroger_279-Sep-10 13:11 

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