SELECT year(CURRENT_DATE()) - year(birth_date) - 
    CASE WHEN month(CURRENT_DATE()) < month(birth_date)
    THEN 1
    ELSE 
        CASE WHEN month(CURRENT_DATE()) = month(birth_date)
        THEN 
            CASE WHEN day(CURRENT_DATE()) < day(birth_date)
            THEN 1
            ELSE 0
            END
        ELSE 0
        END
    END
AS age FROM Students