CREATE FUNCTION dbo.ParseAlphaOnly
(
	@string VARCHAR(8000)
)
RETURNS VARCHAR(8000)
AS
BEGIN
	DECLARE @IncorrectCharLoc SMALLINT
	SET @IncorrectCharLoc = PATINDEX('%[^A-Za-z]%', @string)

	WHILE @IncorrectCharLoc > 0
	BEGIN
		SET @string = STUFF(@string, @IncorrectCharLoc, 1, '')
		SET @IncorrectCharLoc = PATINDEX('%[^A-Za-z]%', @string)
	END

	SET @string = @string
	RETURN @string
END
GO

CREATE FUNCTION dbo.ParseAlphaNumbersOnly
(
	@string VARCHAR(8000)
)
RETURNS VARCHAR(8000)
AS
BEGIN
	DECLARE @IncorrectCharLoc SMALLINT
	SET @IncorrectCharLoc = PATINDEX('%[^0-9A-Za-z]%', @string)

	WHILE @IncorrectCharLoc > 0
	BEGIN
		SET @string = STUFF(@string, @IncorrectCharLoc, 1, '')
		SET @IncorrectCharLoc = PATINDEX('%[^0-9A-Za-z]%', @string)
	END

	SET @string = @string
	RETURN @string
END
GO


CREATE FUNCTION dbo.ParseNumbersOnly
(
	@string VARCHAR(8000)
)
RETURNS VARCHAR(8000)
AS
BEGIN
	DECLARE @IncorrectCharLoc SMALLINT
	SET @IncorrectCharLoc = PATINDEX('%[^0-9]%', @string)

	WHILE @IncorrectCharLoc > 0
	BEGIN
		SET @string = STUFF(@string, @IncorrectCharLoc, 1, '')
		SET @IncorrectCharLoc = PATINDEX('%[^0-9]%', @string)
	END

	SET @string = @string
	RETURN @string
END
GO

--Test
SELECT dbo.ParseAlphaOnly('ABC”_I+{D[]}4|:e;””5,<.F>/?6')
GO
--Result
ABCIDeF

SELECT dbo.ParseAlphaNumbersOnly('ABC”_I+{D[]}4|:e;””5,<.F>/?6')
GO
--Result
ABCID4e5F6


SELECT dbo.ParseNumbersOnly('ABC”_I+{D[]}4|:e;””5,<.F>/?6')
GO
--Result
456