UDF to convert alphanumeric phone numbers to numeric
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User Defined Function (UDF) to convert alphanumeric telephone numbers to numeric numbers

It is very common to use alphabets in phone numbers, in countries like USA. Numbers like "1 800 MICROSOFT", "1 425 MSFAX", "1 800 GO ALAMO" are far too common in States. This often confuses new entrants in USA, and people from other countries, as they have no clue how to convert those characters to numbers!

Sometimes it could be a genuine requirement for an application to convert these alphanumeric phone numbers to numeric ones too. So, here's a User Defined Function (UDF) that does the job. The following code works only in SQL Server 2000. For previous versions like SQL Server 7.0, 6.5 etc., you need to convert this code, to a stored procedure with an output parameter.

The following scalar user defined function accepts a single parameter @pn and converts any characters in that parameter to their corresponding numbers and returns the converted phone number.

	WHERE		ROUTINE_NAME = 'ConvertPhoneNumber'
	DROP FUNCTION dbo.ConvertPhoneNumber

CREATE FUNCTION dbo.ConvertPhoneNumber
	@pn nvarchar(26)
RETURNS nvarchar(26)
	-- Copyright  2002 Narayana Vyas Kondreddi. All rights reserved.
	-- Purpose: To convert alpha numeric phone numbers to numeric
	-- Written by: Narayana Vyas Kondreddi
	-- Site: http://vyaskn.tripod.com
	-- Tested on: SQL Server 2000
	-- Date modified: 17th July 2002 22:50 GMT
	DECLARE @tmp nchar, @n char(26), @idx tinyint

	SET @n = '22233344455566677778889999'
	SET @idx = LEN(@pn)

	WHILE @idx > 0
		SET @tmp = UPPER(SUBSTRING(@pn, @idx, 1))
		IF @tmp BETWEEN 'A' AND 'Z' 
			SET @pn = STUFF(@pn, @idx, 1, SUBSTRING(@n, (ASCII(@tmp)-64), 1))
		SET @idx = @idx - 1
	RETURN @pn 

The following examples show the usage of this function:

Example 1:
SELECT dbo.ConvertPhoneNumber('1 800 Microsoft') AS 'Converted number'

Converted number
1 800 642767638

(1 row(s) affected)

Example 2:
SELECT dbo.ConvertPhoneNumber('1 425 MS FAX') AS 'Converted FAX number'

Converted FAX number
1 425 67 329

(1 row(s) affected)

Example 3:
SELECT dbo.ConvertPhoneNumber(Phone) AS 'Phone Number'
FROM dbo.Customers

Example 4:
DECLARE @Phone varchar(20)
EXEC @Phone = ConvertPhonenumber '1 800 GO ALAMO'
SELECT @Phone AS 'Phone Number'

Phone Number
1 800 46 25266

(1 row(s) affected)

Btw, the above UDF can be used to decode SMS messages into a numeric representation.