Generate Dates in oracle with gaps during Time Period - sql

Question

I Need To Generate Dates During Specific Time Period ( Using Oracle SQL Developer 12& 18).
/
I Found Bellow Solution:
SELECT TO_DATE('01/01/2020','DD/MM/YYYY') + (ROWNUM - 1) DATEGEN
FROM ALL_OBJECTS
WHERE TO_DATE('01/01/2020','DD/MM/YYYY') + (ROWNUM -1) <= TO_DATE('01/11/2020','DD/MM/YYYY')
I Get Daily Dates (As Bellow):
01-JAN-20 12.00.00 AM
02-JAN-20 12.00.00 AM
03-JAN-20 12.00.00 AM
04-JAN-20 12.00.00 AM
05-JAN-20 12.00.00 AM
06-JAN-20 12.00.00 AM
I Need To Get Dates With Gap 5 days or 3 days (Example):
01-JAN-20 12.00.00 AM
05-JAN-20 12.00.00 AM
10-JAN-20 12.00.00 AM
15-JAN-20 12.00.00 AM
Any Suggestions?!
Thanks in Advance.

Answer 1

You can use the hiearchy query with simple logic as follows:
SELECT DATE '2020-01-01' + ( LEVEL * 5 ) - 1
FROM DUAL CONNECT BY
LEVEL <= ( DATE '2020-11-01' - DATE '2020-01-01' ) / 5;
Please note that in your question first two dates have 4 days of difference and in my solution, the First date will be 05-01-2020

Answer 2

You could use a standad recursive query:
with cte (dt) as (
select date '2020-01-01' from dual
union all
select dt + interval '5' day from cte where dt < date '2020-01-15'
)
select * from cte order by dt
You can adjust the boundaries as needed, or move them to another cte:
with
params (startdt, enddt) as (
select date '2020-01-01', date '2020-01-15' from dual
),
cte (dt, enddt) as (
select startdt dt, enddt from params
union all
select dt + interval '5' day, enddt from cte where dt < enddt
)
select dt from cte order by dt
Note that the intervals between the dates are not constant in your sample data (there are 4 days between the first two dates, then 5 days.
You might want to adjust the where clause of the recursive member depending on your actual requirement. Here, the last day may be greater the January 15th. If you don't want that, then change the where clause to:
where dt + interval '5' day < enddt