Oracle 18c

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create table data(
fromTime DATE,
toTime DATE);
insert into data(fromTime, toTime)
values(TO_DATE('2003/05/03 00:00:00', 'yyyy/mm/dd hh24:mi:ss'),
TO_DATE('2003/05/03 02:00:00', 'yyyy/mm/dd hh24:mi:ss'));
1 rows affected

insert into data(fromTime, toTime)
values(TO_DATE('2003/05/03 04:00:00', 'yyyy/mm/dd hh24:mi:ss'),
TO_DATE('2003/05/03 05:00:00', 'yyyy/mm/dd hh24:mi:ss'));
1 rows affected

insert into data(fromTime, toTime)
values(TO_DATE('2003/05/03 15:00:00', 'yyyy/mm/dd hh24:mi:ss'),
TO_DATE('2003/05/03 18:00:00', 'yyyy/mm/dd hh24:mi:ss'));
1 rows affected

insert into data(fromTime, toTime)
values(TO_DATE('2004/05/03 15:00:00', 'yyyy/mm/dd hh24:mi:ss'),
TO_DATE('2004/05/03 18:00:00', 'yyyy/mm/dd hh24:mi:ss'));
1 rows affected

insert into data(fromTime, toTime)
values(TO_DATE('2004/05/03 04:00:00', 'yyyy/mm/dd hh24:mi:ss'),
TO_DATE('2004/05/03 05:00:00', 'yyyy/mm/dd hh24:mi:ss'));
1 rows affected


insert into data(fromTime, toTime)
values(TO_DATE('2003/06/03 00:00:00', 'yyyy/mm/dd hh24:mi:ss'),
TO_DATE('2003/06/03 02:00:00', 'yyyy/mm/dd hh24:mi:ss'));
1 rows affected

SELECT * from data;


FROMTIME
TOTIME


03-MAY-03
03-MAY-03

03-MAY-03
03-MAY-03

03-MAY-03
03-MAY-03

03-MAY-04
03-MAY-04

03-MAY-04
03-MAY-04

03-JUN-03
03-JUN-03


SELECT to_char(fromTime,'DD/MM/YYYY'), sum((toTime-fromTime)*24) from data
group by to_char(fromTime,'DD/MM/YYYY');


TO_CHAR(FROMTIME,'DD/MM/YYYY')
SUM((TOTIME-FROMTIME)*24)


03/05/2003
6

03/05/2004
4

03/06/2003
2

FROMTIME	TOTIME
03-MAY-03	03-MAY-03
03-MAY-03	03-MAY-03
03-MAY-03	03-MAY-03
03-MAY-04	03-MAY-04
03-MAY-04	03-MAY-04
03-JUN-03	03-JUN-03