Returns a formatted phone number

FormatPhoneNumber.sql

CREATE FUNCTION [dbo].[FormatPhoneNumber] (@UnformattedPhoneNumber varchar(50))  
RETURNS varchar(12) 
AS 
BEGIN 
	DECLARE @FormattedPhoneNumber varchar(12) 
	
	SET @FormattedPhoneNumber = REPLACE(REPLACE(@UnformattedPhoneNumber,' ',''),'-','')

	SET @FormattedPhoneNumber = CASE
									WHEN ISNUMERIC(@FormattedPhoneNumber) = 1 AND LEN(@FormattedPhoneNumber) = 10
										THEN SUBSTRING(@FormattedPhoneNumber,1,3) + '-' + SUBSTRING(@FormattedPhoneNumber,4,3) + '-' + SUBSTRING(@FormattedPhoneNumber,7,4)
									WHEN ISNUMERIC(@FormattedPhoneNumber) = 1 AND LEN(@FormattedPhoneNumber) = 7
										THEN SUBSTRING(@FormattedPhoneNumber,1,3) + '-' + SUBSTRING(@FormattedPhoneNumber,4,4)
									ELSE NULL
								END

	
    RETURN  @FormattedPhoneNumber  -- Now Formatted...
END