select t.Month, count(*) Members
from (
select case
when startdate <= to_date('01-Jan-2002', 'DD-MON-YYYY') AND enddate >= to_date('31-Jan-2002', 'DD-MON-YYYY') then ' Jan'
when startdate <= to_date('01-Feb-2002', 'DD-MON-YYYY') AND enddate >= to_date('28-Feb-2002', 'DD-MON-YYYY') then ' Feb'
when startdate <= to_date('01-Mar-2002', 'DD-MON-YYYY') AND enddate >= to_date('31-Mar-2002', 'DD-MON-YYYY') then ' Mar'
when startdate <= to_date('01-Apr-2002', 'DD-MON-YYYY') AND enddate >= to_date('30-Apr-2002', 'DD-MON-YYYY') then ' Apr'
when startdate <= to_date('01-May-2002', 'DD-MON-YYYY') AND enddate >= to_date('31-May-2002', 'DD-MON-YYYY') then ' May'
when startdate <= to_date('01-Jun-2002', 'DD-MON-YYYY') AND enddate >= to_date('30-Jun-2002', 'DD-MON-YYYY') then ' Jun'
when startdate <= to_date('01-Jul-2002', 'DD-MON-YYYY') AND enddate >= to_date('31-Jul-2002', 'DD-MON-YYYY') then ' Jul'
when startdate <= to_date('01-Aug-2002', 'DD-MON-YYYY') AND enddate >= to_date('31-Aug-2002', 'DD-MON-YYYY') then ' Aug'
when startdate <= to_date('01-Sep-2002', 'DD-MON-YYYY') AND enddate >= to_date('30-Sep-2002', 'DD-MON-YYYY') then ' Sep'
when startdate <= to_date('01-Oct-2002', 'DD-MON-YYYY') AND enddate >= to_date('31-Oct-2002', 'DD-MON-YYYY') then ' Oct'
when startdate <= to_date('01-Nov-2002', 'DD-MON-YYYY') AND enddate >= to_date('30-Nov-2002', 'DD-MON-YYYY') then ' Nov'
when startdate <= to_date('01-Dec-2002', 'DD-MON-YYYY') AND enddate >= to_date('31-Dec-2002', 'DD-MON-YYYY') then ' Dec'
end as Month
from member) t
group by t.Month
member
テーブル名はどこにありますか。