I write a paper on this topic comparing queries for PG, SQL Server and
MySQL.
Can you read french ?
http://blog.developpez.com/sqlpro/p9821/langage-sql-norme/agregation-d-intervalles-en-sql-1/
The worst query is the RECURSIVE one !
A +
Le 15/06/2011 17:23, Jira, Marcel a écrit :
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
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