1: SELECT COUNT(id),AVG(Placa) FROM lista_ludnosci WHERE Data_urodzenia>="1960-01-01"and `Data_urodzenia`<="1969-12-31";
2: SELECT plec, COUNT(id),AVG(Placa) FROM `lista_ludnosci` WHERE `Data_urodzenia`>"1960-01-01"and `Data_urodzenia`<"1969-12-31" GROUP by plec