DELIMITER |

CREATE FUNCTION value_economy(gnp_old float, gnp_new float)
RETURNS float
BEGIN
    DECLARE result float;
    DECLARE result1 float;

    SET result1 = (gnp_new - gnp_old) / gnp_old * 100;

    SET result = result1;

        IF(result >= 0) THEN
            SELECT CONCAT("UP");
        ELSE
            SELECT CONCAT("DOWN");
        END IF;

    RETURN result1;

END;|

为什么会出现这种错误？