[Reference] How to replace non numeric string to numeric string

From Here

Prajesh says "a function for you in TSQL doing exactly what you want. It takes 13 secs if you dont use the function for 100,000 records  and 8 secs if you are using functions for same records, so it seems pretty fast."

SELECT Data
FROM TestFunctionPerf --13 sec

SELECT dbo.fnGetNumericOnly(Data) AS Data
FROM TestFunctionPerf -- 8 sec

CREATE FUNCTION fnGetNumericOnly (@string VARCHAR(500))
RETURNS VARCHAR(500)
AS
BEGIN
 DECLARE @NumericOnlyPart VARCHAR(500) = '';
 DECLARE @Numeric VARCHAR(1) = ''
 DECLARE @start INT = 1;
 DECLARE @end INT = 1

 SELECT @end = LEN(@string);

 WHILE (@start <= @end)
 BEGIN
  SET @Numeric = SUBSTRING(@string, @start, @start + 1)

  IF ASCII(@Numeric) >= 48
   AND ASCII(@Numeric) <= 57
  BEGIN
   SET @NumericOnlyPart = @NumericOnlyPart + @Numeric;
  END

  SET @start = @start + 1;
 END

 RETURN @NumericOnlyPart
END
GO

--Test Basic
SELECT dbo.fnGetNumericOnly('12 fgfgf.,jhkjh  khk 56789jhjh67')
GO

--Test on 100,000 Records
CREATE TABLE TestFunctionPerf (Data VARCHAR(8000))
GO

TRUNCATE TABLE TestFunctionPerf
GO

DECLARE @start INT = 1;
DECLARE @end INT = 100000 -- 100,000 Records

WHILE (@start <= @end)
BEGIN
 INSERT INTO TestFunctionPerf
 VALUES ('12 fgfgf.,jhkjh  khk 56789jhjh67')

 SET @start = @start + 1
END
GO

SELECT Data
FROM TestFunctionPerf --13 sec

SELECT dbo.fnGetNumericOnly(Data) AS Data
FROM TestFunctionPerf -- 8 sec