SET GLOBAL log_bin_trust_function_creators=TRUE;
DROP FUNCTION IF EXISTS num_fiter;
CREATE FUNCTION num_fiter(input varchar(255))  RETURNS VARCHAR(255)
BEGIN
    DECLARE i INT;
    DECLARE length INT;    
    DECLARE current VARCHAR(1);
    DECLARE temp VARCHAR(255);
    SET i=0;
    SET temp='';
    SET length=LENGTH(input);

    WHILE i <= length DO
        SET current=SUBSTR(input FROM i FOR 1);
        IF current REGEXP '[0-9]' THEN
            SET current='';
        END IF;
        SET temp=CONCAT(temp,current);
        SET i=i+1;
    END WHILE;
    RETURN temp;
END;

SELECT num_fiter('5456淮南小区');