Pull out most non overlapping date range - sql

Question

Sorry, going to start over and try to explain from the start:
I have a small list of dates:
date mark
08-16-2016 1
08-17-2016 1
01-03-2017 1
02-16-2018 1
02-17-2018 1
From here I need to find out in a 3 year period if there is 2 continuous years where there are less than 3 marks. I'm looking over a date range from 2016-08-01 to 2019-08-01.
So I setup the following query:
with initData as(
select date('2016-08-16') stamp, 1 mark from sysibm.sysdummy1
union select date('2016-08-17') stamp, 1 mark from sysibm.sysdummy1
union select date('2017-01-03') stamp, 1 mark from sysibm.sysdummy1
union select date('2018-02-16') stamp, 1 mark from sysibm.sysdummy1
union select date('2018-02-17') stamp, 1 mark from sysibm.sysdummy1
)
select * from(
select
a.startDate, a.endDate, coalesce(sum(b.mark),0) as mark
from(
select startDate, endDate from(
select stamp startDate, stamp+1 YEAR endDate
from(
select stamp + ym YEAR stamp
from(
select date('2016-08-01') stamp from sysibm.sysdummy1
union
select stamp from initData
union
select stamp+1 DAY from initData
),
(
select 0 as ym from sysibm.sysdummy1
union select 1 as ym from sysibm.sysdummy1
union select 2 as ym from sysibm.sysdummy1
)
)
)
where endDate <= date('2019-08-01')
) a
left outer join(
select stamp, mark from initData
) b
on b.stamp >= a.startDate
and b.stamp < a.endDate
group by a.startDate, a.endDate
)
where mark < 3
order by startDate, endDate
This gives me my list of ranges that I'm looking which have less than 3 marks. Now I need to find full years that don't over lap with other dates.
2016-08-17 2017-08-17 2
2016-08-18 2017-08-18 1
2017-01-03 2018-01-03 1
2017-01-04 2018-01-04 0
2017-08-01 2018-08-01 2
2017-08-16 2018-08-16 2
2017-08-17 2018-08-17 2
2017-08-18 2018-08-18 2
2018-01-03 2019-01-03 2
2018-01-04 2019-01-04 2
2018-02-16 2019-02-16 2
2018-02-17 2019-02-17 1
2018-02-18 2019-02-18 0
2018-08-01 2019-08-01 0
I have finally came up with some solution, but it seems a bit slow and seems like there should be a better way to do it:
with initData as(
select date('2016-08-16') stamp, 1 mark from sysibm.sysdummy1
union select date('2016-08-17') stamp, 1 mark from sysibm.sysdummy1
union select date('2017-01-03') stamp, 1 mark from sysibm.sysdummy1
union select date('2018-02-16') stamp, 1 mark from sysibm.sysdummy1
union select date('2018-02-17') stamp, 1 mark from sysibm.sysdummy1
), dateRanges as(
select startDate, endDate, mark, row_number() over (order by startDate, endDate) rn from(
select
a.startDate, a.endDate, coalesce(sum(b.mark),0) as mark
from(
select startDate, endDate from(
select stamp startDate, stamp+1 YEAR endDate
from(
select stamp + ym YEAR stamp
from(
select date('2016-08-01') stamp from sysibm.sysdummy1
union
select stamp from initData
union
select stamp+1 DAY from initData
),
(
select 0 as ym from sysibm.sysdummy1
union select 1 as ym from sysibm.sysdummy1
union select 2 as ym from sysibm.sysdummy1
)
)
)
where endDate <= date('2019-08-01')
) a
left outer join(
select stamp, mark from initData
) b
on b.stamp >= a.startDate
and b.stamp < a.endDate
group by a.startDate, a.endDate
)
where mark < 3
), dateRangeLimit1 as(
select
a.startDate, a.endDate, a.mark, row_number() over (order by a.startDate, a.endDate) rn
from dateRanges a
left outer join dateRanges b
on a.startDate < b.endDate
and b.rn = 1
and a.rn != b.rn
where b.rn is null
)
select a.* from dateRangeLimit1 a
left outer join dateRangeLimit1 b
on a.startDate < b.endDate
and b.rn = 2 and a.rn <> b.rn and a.rn != 1
where b.rn is null
This gives me back my expected date ranges that don't over lap with each other:
2016-08-17 2017-08-17 2 1
2017-08-17 2018-08-17 2 2
I hope this makes a bit more sense.

Answer 1

I'm not sure your data is quite right, but nonetheless does this help?
WITH D(F,T) AS (VALUES
('2016-08-09','2017-08-09')
,('2016-08-16','2017-08-16')
,('2016-08-17','2017-08-17')
,('2016-08-18','2017-08-18')
,('2017-08-09','2018-08-09')
,('2017-08-16','2018-08-16')
,('2017-08-17','2018-08-17')
,('2017-08-18','2018-08-18')
,('2018-02-16','2019-02-16')
,('2018-02-17','2019-02-17')
,('2018-02-18','2019-02-18')
,('2018-08-09','2019-08-09')
)
SELECT F,T FROM
(
SELECT F,T
, LEAD(F,1) OVER(ORDER BY F ASC) AS NEXT_F
, LAG( T,1) OVER(ORDER BY F ASC) AS PREV_T
FROM D
)
WHERE T >= NEXT_F
OR F <= PREV_T

Answer 2

from dual apparently points to ORACLE.
Find the longest path of non-overlapping (end = start considered non-overlapping) intervals
select level, sys_connect_by_path (startDate || ' .. ' || endDate, '/') path
from blah a
connect by (prior startDate < startDate) and not(prior startDate < endDate and startDate < prior endDate)
order by level desc
-- fetch is 12c+ feature
fetch next 1 rows only;
Using sample data returns
3 /09-AUG-16 .. 09-AUG-17/09-AUG-17 .. 09-AUG-18/09-AUG-18 .. 09-AUG-19
Fiddle