MySQL - Eliminar caracteres

SELECT REGEXP_REPLACE('ALG/12345pppp;/jgh', '[^0-9]+', '');

DELIMITER $$

CREATE FUNCTION `ExtractNumber`(in_string VARCHAR(50))

RETURNS INT

NO SQL

BEGIN

    DECLARE ctrNumber VARCHAR(50);

    DECLARE finNumber VARCHAR(50) DEFAULT '';

    DECLARE sChar VARCHAR(1);

    DECLARE inti INTEGER DEFAULT 1;

    IF LENGTH(in_string) > 0 THEN

        WHILE(inti <= LENGTH(in_string)) DO

            SET sChar = SUBSTRING(in_string, inti, 1);

            SET ctrNumber = FIND_IN_SET(sChar, '0,1,2,3,4,5,6,7,8,9');

            IF ctrNumber > 0 THEN

                SET finNumber = CONCAT(finNumber, sChar);

            END IF;

            SET inti = inti + 1;

        END WHILE;

        RETURN CAST(finNumber AS UNSIGNED);

    ELSE

        RETURN 0;

    END IF;

END$$

DELIMITER ;

SELECT ExtractNumber('ALG/12345pppp;/jgh');