udf_PatExclude8K.sql

IF OBJECT_ID('dbo.udf_PatExclude8K', 'IF') IS NULL
EXECUTE ('CREATE FUNCTION dbo.udf_PatExclude8K() RETURNS TABLE WITH SCHEMABINDING AS RETURN SELECT 1 AS A;');
GO


ALTER FUNCTION dbo.udf_PatExclude8K(
      @String VARCHAR(8000)
    , @Pattern VARCHAR(50)
) 
/*******************************************************************************
 Purpose:
 Given a string (@String) and a pattern (@Pattern) of characters to remove,
 remove the patterned characters from the string.

Usage:
--===== Basic Syntax Example
 SELECT CleanedString 
 FROM dbo.udf_PatExclude8K(@String, @Pattern);

--===== Remove all but Alpha characters
 SELECT CleanedString
 FROM dbo.SomeTable st
 CROSS APPLY dbo.udf_PatExclude8K(st.SomeString,'%[^A-Za-z]%');

--===== Remove all but Numeric digits
 SELECT CleanedString
 FROM dbo.SomeTable st
 CROSS APPLY dbo.udf_PatExclude8K(st.SomeString,'%[^0-9]%');

 Programmer Notes:
 1. @Pattern is not case sensitive (the function can be easily modified to make it so)
 2. There is no need to include the "%" before and/or after your pattern since since we
    are evaluating each character individually

 Revision History:
 Rev 00 - 10/27/2014 Initial Development - Alan Burstein

 Rev 01 - 10/29/2014 Mar 2007 - Alan Burstein
        - Redesigned based on the dbo.STRIP_NUM_EE by Eirikur Eiriksson
          (see: http://www.sqlservercentral.com/Forums/Topic1585850-391-2.aspx)
        - change how the cte tally table is created 
        - put the include/exclude logic in a CASE statement instead of a WHERE clause
        - Added Latin1_General_BIN Colation
        - Add code to use the pattern as a parameter.

 Rev 02 - 11/6/2014
        - Added final performane enhancement (more cudo's to Eirikur Eiriksson)
        - Put 0 = PATINDEX filter logic into the WHERE clause

Rev 03 - 5/16/2015
        - Updated code to deal with special XML characters
*******************************************************************************/
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
WITH E1(N) AS (
SELECT N
FROM (VALUES (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)) AS X(N)
),
iTally(N) AS
(
  SELECT TOP(CONVERT(INT,LEN(@String),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
  FROM E1 T1 CROSS JOIN E1 T2 CROSS JOIN E1 T3 CROSS JOIN E1 T4
) 
SELECT NewString =
((
  SELECT SUBSTRING(@String,N,1)
  FROM iTally
  WHERE 0 = PATINDEX(@Pattern,SUBSTRING(@String COLLATE Latin1_General_BIN,N,1))
  FOR XML PATH(''),TYPE
).value('.[1]','varchar(8000)'));
GO