Date: Thu, 27 May 2010 14:45:15 +0200
From: "A. Kretschmer" <andreas.kretschmer@schollglas.com>
To: pgsql-sql@postgresql.org
Subject: Re: Check set of date intervals
Message-ID: <20100527124515.GE6907@a-kretschmer.de>
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In response to Anton Gavazuk :
> Hi Andreas,
> 
> great thanks for the response,

please, answer to the list, not to me, okay?


> 
> unfortunately function just tests every row  - it doesnt construct set of
> periods which would cover choosed period.

That's hard to achieve ... maybe you have to create a table with
contiguous periods. Somewhere i have found this code-snippet:

test=*# select * from t1;
 a
----
  1
  2
  3
  4
  6
  7
  8
 10
 11
 12
 13
(11 rows)

test=*# WITH RECURSIVE RecCols (LeftBoundary, Value) AS
  (SELECT a, a FROM t1 WHERE (a - 1) NOT IN (SELECT a FROM t1)
   UNION ALL SELECT p.LeftBoundary, c.a FROM RecCols AS p, t1 AS c WHERE c.a = p.Value + 1)
  SELECT LeftBoundary, MAX(Value) AS RightBoundary FROM RecCols
    GROUP BY LeftBoundary
    ORDER BY LeftBoundary;
 leftboundary | rightboundary
--------------+---------------
            1 |             4
            6 |             8
           10 |            13
(3 rows)

Maybe that's the way you have to go ...


Andreas
-- 
Andreas Kretschmer
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