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Re: Merge overlapping time-periods - Mailing list pgsql-sql

From Oliveiros d'Azevedo Cristina
Subject Re: Merge overlapping time-periods
Date
Msg-id D5459212DE8D4037AA3B3AC0892ED3C2@marktestcr.marktest.pt
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In response to Merge overlapping time-periods  ("Jira, Marcel" <Marcel.Jira@wu.ac.at>)
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Hello again, Marcel.
 
I tried this and it seems to work on the example you provided, iif my understanding is correct and you want the ID=2 to have just one record on final output.
That makes sense to me because

2   2000-01-15   2000-03-31

2   2000-04-01   2000-04-15

 

are in direct sequence (IMHO) as much as

1 2000-01-01   2000-03-31

1   2000-04-01   2000-05-31

 

are. Isn't my understanding correct?

 

Best,

Oliveiros

 
(SELECT x."ID",x."BEG",x."END"
FROM mytable x
LEFT JOIN
(
SELECT a."ID" as xid ,a."BEG" as xbeg,a."END" as xend,b."ID" as yid,b."BEG" as ybeg,b."END" as yend
FROM mytable a
JOIN mytable b
ON a."ID"  = b."ID"
AND (( ((a."BEG",a."END") OVERLAPS (b."BEG",b."END"))
OR ((b."BEG" - a."END") = 1))
AND (a."BEG" <> b."BEG")
AND (b."END" <> a."END"))
) y
ON (((yid = x."ID")
AND (ybeg = x."BEG")
AND (yend = x."END"))
OR ((xid = x."ID")
AND (xbeg = x."BEG")
AND (xend = x."END")))
 

WHERE yid IS NULL)
UNION (
SELECT x."ID",MIN(x."BEG"),MAX(x."END")
FROM mytable x
LEFT JOIN
(
SELECT a."ID" as xid,a."BEG" as xbeg,a."END" as xend,b."ID" as yid,b."BEG" as ybeg,b."END" as yend
FROM mytable a
JOIN mytable b
ON a."ID"  = b."ID"
AND (( ((a."BEG",a."END") OVERLAPS (b."BEG",b."END"))
OR ((a."BEG" - b."END") = 1))
AND (a."BEG" <> b."BEG")
AND (b."END" <> a."END"))
) y
ON (((yid = x."ID")
AND (ybeg = x."BEG")
AND (yend = x."END"))
OR ((xid = x."ID")
AND (xbeg = x."BEG")
AND (xend = x."END")))
 
WHERE yid IS NOT NULL
GROUP BY x."ID"
)

Howdy, Marcel,
 
In the example output you provided the ID = 2 should have just one record...Ain't I right?
 
Best,
Oliveiros
----- Original Message -----
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

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