Re: Merge overlapping time-periods

----- Original Message -----

From: Jira, Marcel

To: 'pgsql-sql@postgresql.org'

Sent: Wednesday, June 15, 2011 4:23 PM

Subject: [SQL] Merge overlapping time-periods

Hi!

 

Although I try for some time, I am not able to write an SQL-Query that can do the following:

 

I have a very big table (let’s call it “mytable”) with information like this:

 

ID  BEG          END

1   2000-01-01   2000-03-31

1   2000-04-01   2000-05-31

1   2000-04-15   2000-07-31

1   2000-09-01   2000-10-31

2   2000-02-01   2000-03-15

2   2000-01-15   2000-03-31

2   2000-04-01   2000-04-15

3   2000-06-01   2000-06-15

3   2000-07-01   2000-07-15

 

There’s an ID and time periods defined by a start value (BEG) and an end value (END)

 

I want to merge all periods belonging to the same ID, iff their time periods are overlapping or in a direct sequence.

 

Therefore the result should somehow look like this:

 

ID  BEG          END

1   2000-01-01   2000-07-31

1   2000-09-01   2000-10-31

2   2000-01-15   2000-03-31

2   2000-04-01   2000-04-15

3   2000-06-01   2000-06-15

3   2000-07-01   2000-07-15

 

I tried using “WITH RECURSIVE” but I didn’t succeed.

 

My server is PostgreSQL 8.4. Unfortunately I can’t do anything like update or install some fancy module…

 

Thank you for your help!

 

Best regards,

 

Marcel Jira