id = id_ju1
registration date =date_regis
table = master

SELECT count(DISTINCT(id_ju1)),
CASE
WHEN month(date_regis) >=1 and month(date_regis) <=3 THEN 'jun-mar'
WHEN  month(date_regis) >=4 and month(date_regis) <=6 THEN 'mar-jun' END
FROM master