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stumped on a with recursive example

From: Henry Drexler <alonup8tb(at)gmail(dot)com>
To: PGSQL-Novice <pgsql-novice(at)postgresql(dot)org>
Subject: stumped on a with recursive example
Date: 2011-12-02 15:12:52
Message-ID: CAAtgU9TxRQBkNDAh=UD7WHLSCnVaOVcjrM6+6LBFw8NmmbfLNQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-novice
on http://wiki.postgresql.org/wiki/CTEReadme

It shows this:

INSERT INTO department (id, parent_department, "name")
VALUES
     (0, NULL, 'ROOT'),
     (1, 0, 'A'),
     (2, 1, 'B'),
     (3, 2, 'C'),
     (4, 2, 'D'),
     (5, 0, 'E'),
     (6, 4, 'F'),
     (7, 5, 'G');

-- department structure represented here is as follows:
--
-- ROOT-+->A-+->B-+->C
--      |         |
--      |         +->D-+->F
--      +->E-+->G


I have ran the recursive query and indeed it only is showing A,B,C,D,F and
not E,G as shown in the graphic above.  So postgres is understanding the
structure - however I am not.

What I am not getting/seeing is how one is getting the F to come after the
D and the G after the E.

  I can see A and E both have a 0 so they branch off of the Null, but why
is the 4,'F' being attached to the 2,'D' and the 5,'G' being attached to
the 0,'E'?

Responses

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Next:From: Johan NelDate: 2011-12-02 15:29:44
Subject: Re: stumped on a with recursive example
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Subject: Why tuning is not giving better performance?

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