codice:
select count(*) as iscritti,
CASE
WHEN ( YEAR(CURRENT_DATE)-YEAR(data))- ( RIGHT(CURRENT_DATE,5)< RIGHT(data,5) ) BETWEEN 14 AND 18 THEN "14-18"
WHEN ( YEAR(CURRENT_DATE)-YEAR(data))- ( RIGHT(CURRENT_DATE,5)< RIGHT(data,5) ) BETWEEN 19 AND 25 THEN "19-25"
ELSE "altro"
END as fascia
FROM tabella
GROUP BY fascia