Detect overlapping date ranges from the same table

Question

I have a table with the following data

PKey  Start       End         Type
====  =====       ===         ====
01    01/01/2010  14/01/2010  S
02    15/01/2010         


        

Answer 1

BTW - If you don't have a unique id , against your dates you can do this is oracle..FYI

with date_ranges
as
(
SELECT 
     rownum as pkey,
    date_ranges.*
FROM  date_ranges
) 
select 
dr1.* 
from 
date_ranges dr1 , date_ranges dr2
where  dr1.pkey > dr2.pkey
AND dr1.end_dt >= dr2.start_dt 
AND dr2.end_dt >= dr1.start_dt

Answer 2

When I needed to compare two time spans in SQL for overlap, here are the four scenarios I could think of:

1. Span1 start is between Span2 start and Span2 end
2. Span1 end is between Span2 start and Span2 end
3. Span1 start and end are both between Span2 start and Span2 end
4. Span2 start and end are both between Span1 start and Span1 end

Here is the OR statement I created to capture these scenarios (in my case Oracle SQL):

and (
    s1.start between s2.start and s2.end
    OR
    s1.end between s2.start and s2.end
    OR
    s2.start between s1.start and s1.end
)

Answer 3

In MySQL you basically need:

SELECT COUNT(*) FROM date_ranges AS A, date_ranges AS B WHERE A.id <> B.id AND A.id > B.id AND A.end_at > B.start_at AND B.end_at > A.start_at

> in the second and the third statement can be replaced with >= to follow includes matching.

This topic is related to the "Allen's Interval Algebra" and there are some more reading on this can be found by those links:

• http://www.ics.uci.edu/~alspaugh/cls/shr/allen.html
• http://salman-w.blogspot.com.es/2012/06/sql-query-overlapping-date-ranges.html

Answer 4

Perhaps:

SELECT A.PKey, A.Start, A.End, A.Type
FROM calendar AS A, calendar AS B
WHERE (p.pkey<>a.pkey
AND b.start>=a.start
AND b.end<=a.end)
OR (b.pkey<>a.pkey
AND b.start<=a.start
AND b.end>=a.end)

Answer 5

We've all needed this kind of overlapping predicate in our queries for quite some time and I think I've found a really simple solution here.

In my application, as an example, I have policies that have the same Policy Number but maybe the Policy Description changes from one fiscal year to the next. When a user is entering a new record (same Policy Number, different Policy Description), I needed a way to tell if that policy already exists for the specified time range. If the new Policy Effective/Expiration dates overlap with whatever is already in the database, I needed to error out and tell the user why their input was not correct.

To do this, I went with the following predicate statement:

AND @_expiration >= EffectiveDate AND ExpirationDate >= @_effective

Hopefully someone else finds this as useful as I have.

Answer 6

I had to do a very similar thing for to stop duplicate holiday being entered into a table. it was in access and written to a temptable on input so had to query it in VBA SQL:

 stCommandText = "SELECT " _
                    & "* " _
                    & "FROM " _
                    & "TableName a, " _
                    & "TableName b " _
                    & "WHERE " _
                    & "a.ID = b.ID " _
                    & "AND a.Startdate >= b.Startdate AND a.StartDate <= b.EndDate " _
                    & "AND a.AutoNo <> b.AutoNo "