Finding correct date pair and eliminate the overlapped one in T-SQL - sql

Question

I have a Dates like startdate as one column and Enddate as another column. I need to find eliminate Continuous date ranges in data in sQL.I need to find the overlapped items and i need to delete.I already using one code to find Overlap items.And i am giving startdate and enddate as parameter.
Code i am using to find overlap
Select * from #t
where
((cast(#StartDate as datetime2)>=StartDate and cast(#EndDate as datetime2)<=EndDate)
OR (StartDate>= cast(#StartDate as datetime2) and EndDate<= cast(#EndDate as datetime2))
OR (cast(#StartDate as datetime2)>=StartDate AND cast(#StartDate as datetime2)<=EndDate)
OR (cast(#EndDate as datetime2)>=StartDate AND cast(#EndDate as datetime2)<=EndDate))
Above query is ok to find normal overlap like
Id
Startdate
Enddate
1
01/01/2020
01/11/2020
2
01/01/2020
01/03/2021
In above condition i will delete one data and i will keep other one
But it fails in below type of data example.When run for below type of query 1 id is overlapped with 2 and 2 is overlapped with both 1 and 3.So it show both 1 and 2 to delete.but in my case is not to delete 1 and 3.only 2 need to be deleted.since 2 is overlapped between both data and 1& 3 is already in good date periods
For example
Id
Startdate
Enddate
1
01/01/2020
01/11/2020
2
01/01/2020
01/03/2021
3
02/11/2020
05/04/2022
In above example we have three pair of dates and id 1 and 3 are in correct interval and 2 is overlapped between both id. I need to find overlapped one or non overlapped items. Any case is ok for me to find the result.
My Expected Result is
Id
Startdate
Enddate
2
01/01/2020
01/03/2021
Another example is
Id
Startdate
Enddate
1
01/01/2020
01/11/2020
2
02/11/2020
06/05/2022
3
02/11/2020
05/04/2022
Above if you see 1 and 2 is in correct date periods but id 3 is overlapped with 2 id.Now i want to find only that overlapped result and i don't need other data.
Another example is
Id
Startdate
Enddate
3
02/11/2020
05/04/2022

Answer 1

I used second set of data, But this should work for first set of data as well. But I have a doubt on your first record set expected output. If you can clear it up, i can check again,
Create table OverlapData_1
(
id int
, Startdate date
, EndDate date
)
insert into OverlapData_1 values(1, '01/01/2020','01/11/2020')
insert into OverlapData_1 values(2, '01/01/2020','01/03/2021')
insert into OverlapData_1 values(3, '02/11/2020','05/04/2022')
SELECT A.[id]
,A.Startdate
,A.EndDate FROM
(
SELECT
CASE WHEN Startdate between LAG(StartDate) OVER ( order by id) and LAG(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_1]
, CASE WHEN EndDate between LAG(StartDate) OVER ( order by id) and LAG(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_2]
, CASE WHEN StartDate between LEAD(StartDate) OVER ( order by id) and LEAD(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_3]
, CASE WHEN EndDate between LEAD(StartDate) OVER ( order by id) and LEAD(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_4]
,*
FROM OverlapData_1
) AS A
WHERE (A.status_1 = 1 AND A.status_2 = 1)
OR (A.status_1 = 1 AND A.status_4 = 1)
Create table OverlapData_2
(
id int
, Startdate date
, EndDate date
)
insert into OverlapData_2 values(1, '01/01/2020','01/11/2020')
insert into OverlapData_2 values(2, '01/01/2020','06/05/2022')
insert into OverlapData_2 values(3, '02/11/2020','05/04/2022')
SELECT A.[id]
,A.Startdate
,A.EndDate FROM
(
SELECT
CASE WHEN Startdate between LAG(StartDate) OVER ( order by id) and LAG(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_1]
, CASE WHEN EndDate between LAG(StartDate) OVER ( order by id) and LAG(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_2]
, CASE WHEN StartDate between LEAD(StartDate) OVER ( order by id) and LEAD(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_3]
, CASE WHEN EndDate between LEAD(StartDate) OVER ( order by id) and LEAD(EndDate) OVER ( order by id) THEN 1 else 0 end as [status_4]
,*
FROM OverlapData_2
) AS A
WHERE (A.status_1 = 1 AND A.status_2 = 1)
OR (A.status_1 = 1 AND A.status_4 = 1)