Oracle 18c

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create table the_table (time_of_day timestamp, hours_to_add numeric);
insert into the_table values (timestamp '2020-10-01 22:15:00', 3);
1 rows affected

insert into the_table values (timestamp '2020-11-01 15:04:00', 4);
1 rows affected

select to_char(time_of_day, 'yyyy-mm-dd hh24:mi:ss') as time_of_day,
       hours_to_add,
       to_char(time_of_day + interval '1' hour * hours_to_add, 'yyyy-mm-dd hh24:mi:ss') as new_time
from the_table;


TIME_OF_DAY
HOURS_TO_ADD
NEW_TIME


2020-10-01 22:15:00
3
2020-10-02 01:15:00

2020-11-01 15:04:00
4
2020-11-01 19:04:00

TIME_OF_DAY	HOURS_TO_ADD	NEW_TIME
2020-10-01 22:15:00	3	2020-10-02 01:15:00
2020-11-01 15:04:00	4	2020-11-01 19:04:00