An Easy But Effective Way to Split a String using Transact-SQL

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Introduction

In this article, I will demonstrate how to split a string using Transact-SQL.

Background

String manipulation is pretty interesting for most software developers. To split a string by using a user defined delimiter is nothing new for programmers. Even Microsoft .NET Frameworks provide us a huge "Standard Techniques" for doing this. But if we want to split a string using Transact -SQL, then how can we achieve this?

Using the Code

It is very simple to use. We just need some basic concepts on the following:

• CHARINDEX
• SUBSTRING

CHARINDEX

Returns the starting position of the specified expression in a character string.

Syntax

CHARINDEX ( expression1 , expression2 [ , start_location ] ) 

Arguments

expression1: An expression containing the sequence of characters to be found. expression1 is an expression of the short character data type category.

expression2: An expression, usually a column searched for the specified sequence. expression2 is of the character string data type category.

start_location: The character position to start searching for expression1 in expression2. If start_location is not given, is a negative number, or is zero, the search starts at the beginning of expression2.

Return Types: int

Example

USE pubs
GO
SELECT CHARINDEX('wonderful', notes)
FROM titles
WHERE title_id = 'TC3218'
GO

More details can be found at this link.

SUBSTRING

Returns part of a character, binary, text, or image expression for more information about the valid Microsoft® SQL Server™ data types that can be used with this function.

Syntax

SUBSTRING ( expression , start , length ) 

Arguments

Expression: A character string, binary string, text, image, a column, or an expression that includes a column. Do not use expressions that include aggregate functions.

Start: An integer that specifies where the SUBSTRING begins.

Length: An integer that specifies the length of the SUBSTRING (the number of characters or bytes to return).

Note: Because start and length specify the number of bytes when SUBSTRING is used on text data, DBCS data, such as Kanji, may result in split characters at the beginning or end of the result. This behavior is consistent with the way in which READTEXT handles DBCS. However, because of the occasional strange result, it is advisable to use ntext instead of text for DBCS characters.

Return Types: Returns character data if expression is one of the supported character data types. Returns binary data if expression is one of the supported binary data types.

Example

USE pubs
SELECT au_lname, SUBSTRING(au_fname, 1, 1)
FROM authors
ORDER BY au_lname

More details can be found at this link.

I wrote a simple function named SPLITE which will split an expression using CHARINDEX and SUBSTRING functions. A sample code example is given below:

Sample Example

            set QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: Md. Marufuzzaman
-- Create date: 
-- Description: Split an expression. 
-- Note: If you are using SQL Server 2000, You need to change the 
-- length (MAX) to your maximum expression length of each datatype.
-- =============================================
/*
SELECT * FROM [dbo].[SPLIT] (';','I love codeProject;!!!;Your development resources')
*/
CREATE FUNCTION [dbo].[SPLIT] 
   (  @DELIMITER VARCHAR(5), 
      @LIST      VARCHAR(MAX) 
   ) 
   RETURNS @TABLEOFVALUES TABLE 
      (  ROWID   SMALLINT IDENTITY(1,1), 
         [VALUE] VARCHAR(MAX) 
      ) 
AS 
   BEGIN
    
      DECLARE @LENSTRING INT 
 
      WHILE LEN( @LIST ) > 0 
         BEGIN 
         
            SELECT @LENSTRING = 
               (CASE CHARINDEX( @DELIMITER, @LIST ) 
                   WHEN 0 THEN LEN( @LIST ) 
                   ELSE ( CHARINDEX( @DELIMITER, @LIST ) -1 )
                END
               ) 
                                
            INSERT INTO @TABLEOFVALUES 
               SELECT SUBSTRING( @LIST, 1, @LENSTRING )
                
            SELECT @LIST = 
               (CASE ( LEN( @LIST ) - @LENSTRING ) 
                   WHEN 0 THEN '' 
                   ELSE RIGHT( @LIST, LEN( @LIST ) - @LENSTRING - 1 ) 
                END
               ) 
         END
          
      RETURN 
      
   END

Note: I have used some other functions like LNE(), LEFT(), etc. which are very common and I hope that everyone is very much familiar with this. Hence, I did not include this. Actually I do not want to lose focus on the main objective of this article.

Conclusion

I hope that this article might be helpful to you. Enjoy!

History

• 9^th August 2009: Initial post