From: Joe Conway <mail@joeconway.com>
To: Camila Rocha <camilarrocha@hotmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: rows in order
Date: Fri, 04 Oct 2002 08:51:42 -0700
Message-ID: <3D9DB90E.3010101@joeconway.com> (raw)
References: <OE40vN3qljWwY0VnkB4000054b0@hotmail.com>
Camila Rocha wrote:
> Is there a way to put in order the rows in a table? the problem is that i w=
> ant to keep a "tree" in the db, but the leaves must be ordered...
> does someone have an idea?
If you don't mind trying 7.3 beta, there is a function called connectby() in
contrib/tablefunc. It works like this:
CREATE TABLE connectby_tree(keyid text, parent_keyid text);
INSERT INTO connectby_tree VALUES('row1',NULL);
INSERT INTO connectby_tree VALUES('row2','row1');
INSERT INTO connectby_tree VALUES('row3','row1');
INSERT INTO connectby_tree VALUES('row4','row2');
INSERT INTO connectby_tree VALUES('row5','row2');
INSERT INTO connectby_tree VALUES('row6','row4');
INSERT INTO connectby_tree VALUES('row7','row3');
INSERT INTO connectby_tree VALUES('row8','row6');
INSERT INTO connectby_tree VALUES('row9','row5');
SELECT * FROM
connectby('connectby_tree', 'keyid', 'parent_keyid', 'row2', 0, '~')
AS t(keyid text, parent_keyid text, level int, branch text);
keyid | parent_keyid | level | branch
-------+--------------+-------+---------------------
row2 | | 0 | row2
row4 | row2 | 1 | row2~row4
row6 | row4 | 2 | row2~row4~row6
row8 | row6 | 3 | row2~row4~row6~row8
row5 | row2 | 1 | row2~row5
row9 | row5 | 2 | row2~row5~row9
(6 rows)
This allows completely dynamically generated trees.
There is also a contrib/ltree, which I believe creates a persistent structure
for the tree information, and gives you tools to manipulate it (but I have
never used it, so my discription may not be completely accurate).
HTH,
Joe
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Subject: Re: rows in order
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