Oracle 11g Release 2

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create table test (
id number(10),
start_date timestamp,
end_date timestamp);
insert into test values(1, to_date('01.01.2019', 'dd.mm.yyyy'),  to_date('03.01.2019', 'dd.mm.yyyy'));
1 rows affected

insert into test values(2, to_date('02.01.2019', 'dd.mm.yyyy'),  to_date('05.01.2019', 'dd.mm.yyyy'));
1 rows affected

insert into test values(3, to_date('04.01.2019', 'dd.mm.yyyy'),  to_date('06.01.2019', 'dd.mm.yyyy'));
1 rows affected

SELECT dt.mydate, COUNT(DISTINCT id) cnt
FROM
    ( SELECT DISTINCT start_date mydate FROM test UNION ALL SELECT DISTINCT end_date  FROM test ) dt
    LEFT JOIN test t ON dt.mydate >= t.start_date AND dt.mydate <= t.end_date
GROUP BY dt.mydate
ORDER BY dt.mydate


MYDATE
CNT


01-JAN-19 12.00.00.000000 AM
1

02-JAN-19 12.00.00.000000 AM
2

03-JAN-19 12.00.00.000000 AM
2

04-JAN-19 12.00.00.000000 AM
2

05-JAN-19 12.00.00.000000 AM
2

06-JAN-19 12.00.00.000000 AM
1

MYDATE	CNT
01-JAN-19 12.00.00.000000 AM	1
02-JAN-19 12.00.00.000000 AM	2
03-JAN-19 12.00.00.000000 AM	2
04-JAN-19 12.00.00.000000 AM	2
05-JAN-19 12.00.00.000000 AM	2
06-JAN-19 12.00.00.000000 AM	1