Получаем возраст в годах
CREATE FUNCTION `AgeYears` (Birthday DATE) RETURNS INT(3) No SQL
BEGIN
RETURN YEAR(CURRENT_DATE)-YEAR(Birthday) - ((month(CURRENT_DATE)<month(Birthday)) OR
(month(CURRENT_DATE)=month(Birthday) AND day(CURRENT_DATE)<day(Birthday)));
END
Получаем возрастной период...