T-SQL strip all non-alpha and non-numeric characters - sql-server-2008

Question

Is there a smarter way to remove all special characters rather than having a series of about 15 nested replace statements?
The following works, but only handles three characters (ampersand, blank and period).
select CustomerID, CustomerName,
Replace(Replace(Replace(CustomerName,'&',''),' ',''),'.','') as CustomerNameStripped
from Customer

Answer 1

One flexible-ish way;
CREATE FUNCTION [dbo].[fnRemovePatternFromString](#BUFFER VARCHAR(MAX), #PATTERN VARCHAR(128)) RETURNS VARCHAR(MAX) AS
BEGIN
DECLARE #POS INT = PATINDEX(#PATTERN, #BUFFER)
WHILE #POS > 0 BEGIN
SET #BUFFER = STUFF(#BUFFER, #POS, 1, '')
SET #POS = PATINDEX(#PATTERN, #BUFFER)
END
RETURN #BUFFER
END
select dbo.fnRemovePatternFromString('cake & beer $3.99!?c', '%[$&.!?]%')
(No column name)
cake beer 399c

Answer 2

Create a function:
CREATE FUNCTION dbo.StripNonAlphaNumerics
(
#s VARCHAR(255)
)
RETURNS VARCHAR(255)
AS
BEGIN
DECLARE #p INT = 1, #n VARCHAR(255) = '';
WHILE #p <= LEN(#s)
BEGIN
IF SUBSTRING(#s, #p, 1) LIKE '[A-Za-z0-9]'
BEGIN
SET #n += SUBSTRING(#s, #p, 1);
END
SET #p += 1;
END
RETURN(#n);
END
GO
Then:
SELECT Result = dbo.StripNonAlphaNumerics
('My Customer''s dog & #1 friend are dope, yo!');
Results:
Result
------
MyCustomersdog1friendaredopeyo
To make it more flexible, you could pass in the pattern you want to allow:
CREATE FUNCTION dbo.StripNonAlphaNumerics
(
#s VARCHAR(255),
#pattern VARCHAR(255)
)
RETURNS VARCHAR(255)
AS
BEGIN
DECLARE #p INT = 1, #n VARCHAR(255) = '';
WHILE #p <= LEN(#s)
BEGIN
IF SUBSTRING(#s, #p, 1) LIKE #pattern
BEGIN
SET #n += SUBSTRING(#s, #p, 1);
END
SET #p += 1;
END
RETURN(#n);
END
GO
Then:
SELECT r = dbo.StripNonAlphaNumerics
('Bob''s dog & #1 friend are dope, yo!', '[A-Za-z0-9]');
Results:
r
------
Bobsdog1friendaredopeyo

Answer 3

I faced this problem several years ago, so I wrote a SQL function to do the trick. Here is the original article (was used to scrape text out of HTML). I have since updated the function, as follows:
IF (object_id('dbo.fn_CleanString') IS NOT NULL)
BEGIN
PRINT 'Dropping: dbo.fn_CleanString'
DROP function dbo.fn_CleanString
END
GO
PRINT 'Creating: dbo.fn_CleanString'
GO
CREATE FUNCTION dbo.fn_CleanString
(
#string varchar(8000)
)
returns varchar(8000)
AS
BEGIN
---------------------------------------------------------------------------------------------------
-- Title: CleanString
-- Date Created: March 26, 2011
-- Author: William McEvoy
--
-- Description: This function removes special ascii characters from a string.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
declare #char char(1),
#len int,
#count int,
#newstring varchar(8000),
#replacement char(1)
select #count = 1,
#len = 0,
#newstring = '',
#replacement = ' '
---------------------------------------------------------------------------------------------------
-- M A I N P R O C E S S I N G
---------------------------------------------------------------------------------------------------
-- Remove Backspace characters
select #string = replace(#string,char(8),#replacement)
-- Remove Tabs
select #string = replace(#string,char(9),#replacement)
-- Remove line feed
select #string = replace(#string,char(10),#replacement)
-- Remove carriage return
select #string = replace(#string,char(13),#replacement)
-- Condense multiple spaces into a single space
-- This works by changing all double spaces to be OX where O = a space, and X = a special character
-- then all occurrences of XO are changed to O,
-- then all occurrences of X are changed to nothing, leaving just the O which is actually a single space
select #string = replace(replace(replace(ltrim(rtrim(#string)),' ', ' ' + char(7)),char(7)+' ',''),char(7),'')
-- Parse each character, remove non alpha-numeric
select #len = len(#string)
WHILE (#count <= #len)
BEGIN
-- Examine the character
select #char = substring(#string,#count,1)
IF (#char like '[a-z]') or (#char like '[A-Z]') or (#char like '[0-9]')
select #newstring = #newstring + #char
ELSE
select #newstring = #newstring + #replacement
select #count = #count + 1
END
return #newstring
END
GO
IF (object_id('dbo.fn_CleanString') IS NOT NULL)
PRINT 'Function created.'
ELSE
PRINT 'Function NOT created.'
GO

Answer 4

I know this is an old thread, but still, might be handy for others.
Here's a quick and dirty (Which I've done inversely - stripping out non-numerics) - using a recursive CTE.
What makes this one nice for me is that it's an inline function - so gets around the nasty RBAR effect of the usual scalar and table-valued functions.
Adjust your filter as needs be to include or exclude whatever char types.
Create Function fncV1_iStripAlphasFromData (
#iString Varchar(max)
)
Returns
Table With Schemabinding
As
Return(
with RawData as
(
Select #iString as iString
)
,
Anchor as
(
Select Case(IsNumeric (substring(iString, 1, 1))) when 1 then substring(iString, 1, 1) else '' End as oString, 2 as CharPos from RawData
UNION ALL
Select a.oString + Case(IsNumeric (substring(#iString, a.CharPos, 1))) when 1 then substring(#iString, a.CharPos, 1) else '' End, a.CharPos + 1
from RawData r
Inner Join Anchor a on a.CharPos <= len(rtrim(ltrim(#iString)))
)
Select top 1 oString from Anchor order by CharPos Desc
)
Go
select * from dbo.fncV1_iStripAlphasFromData ('00000')
select * from dbo.fncV1_iStripAlphasFromData ('00A00')
select * from dbo.fncV1_iStripAlphasFromData ('12345ABC6789!&*0')

Answer 5

If you can use SQL CLR you can use .NET regular expressions for this.
There is a third party (free) package that includes this and more - SQL Sharp .