How to retrive/get all the numbers from a string using SQL server

Script for getting all the numbers from string

DECLARE @string1 varchar(100)='welcome2sql1239hello23';

DECLARE @string2 varchar(100)='',@i int=0;

WHILE @i<=LEN(@string1)

BEGIN

IF(SUBSTRING(@string1,@i,1)>='0' AND SUBSTRING(@string1,@i,1)<='9')

SET @string2=@string2+SUBSTRING(@string1,@i,1);

SET @i=@i+1;

END

SELECT @string2 AS [Numbers obtained];