I have the following data. I have looked over a lot of threads about overlapping and non-overlapping dates but none seemed to help me.
=============================== PK | StartDate | EndDate =============================== 1 | 2016-05-01 | 2016-05-02 2 | 2016-05-02 | 2016-05-03 3 | 2016-05-03 | 2016-05-04 4 | 2016-05-04 | 2016-05-05 5 | 2016-05-07 | 2016-06-08 ===============================
From this table with a SQL query I want to return the first record out of overlapping dates or basically
=============================== PK | StartDate | EndDate =============================== 1 | 2016-05-01 | 2016-05-02 3 | 2016-05-03 | 2016-05-04 5 | 2016-05-07 | 2016-06-08 ===============================
I have been struggling a lot with this query and was wondering if this is actually possible without too much of a hit on performance and whether its better if thats done on backend or with a SQL query because I believe it’d be easier for me to do it on the backend.
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Answer
This can be achieved by creating a new column and partitioning it to fetch only first rows.
declare @tbl table
(pk int identity,StartDate date,EndDate date)
insert into @tbl
values('2016-05-01','2016-05-02')
,('2016-05-02','2016-05-03')
,('2016-05-03','2016-05-04')
,('2016-05-04','2016-05-05')
,('2016-05-07','2016-06-08')
select pk,startdate,enddate from(select pk,startdate,enddate
,ROW_NUMBER()over(partition by [overlappingdates] order by startdate)rn
from(
select *,case when ROW_NUMBER()over(order by startdate) % 2 = 0
then StartDate else EndDate end as [overlappingdates]
from
@tbl
)t
)t
where t.rn = 1