Thread: rows in order
Hi!
Is there a way to put in order the rows in a table? the problem is that i want to keep a "tree" in the db, but the leaves must be ordered...
does someone have an idea?
thanks,
Camila
How do you plan to keep your tree represented?? There are quite a few options for this. Extensive talk has been made in this list. Also search the archives. Basically you can follow - nested trees (pure sql) aproach - Genealogical tree representation approach(either using text to represent the path to the parent (pure sql), orarrays) - The contrib/tree implementation ================================================================== Achilleus Mantzios S/W Engineer IT dept Dynacom Tankers Mngmt Nikis 4, Glyfada Athens 16610 Greece tel: +30-10-8981112 fax: +30-10-8981877 email: achill@matrix.gatewaynet.com mantzios@softlab.ece.ntua.gr
On Monday 30 Sep 2002 7:29 pm, Camila Rocha wrote: > Hi! > > Is there a way to put in order the rows in a table? the problem is that i > want to keep a "tree" in the db, but the leaves must be ordered... does > someone have an idea? Do a search on "Joe Celko" and "tree" and you should find a clean way to model trees in SQL. -- Richard Huxton
On Fri, 4 Oct 2002, Achilleus Mantzios wrote: > > How do you plan to keep your tree represented?? > > There are quite a few options for this. > Extensive talk has been made in this list. > Also search the archives. > Basically you can follow > - nested trees (pure sql) aproach > - Genealogical tree representation approach > (either using text to represent the path to the parent (pure sql), or > arrays) > - The contrib/tree implementation contrib/ltree ! > > ================================================================== > Achilleus Mantzios > S/W Engineer > IT dept > Dynacom Tankers Mngmt > Nikis 4, Glyfada > Athens 16610 > Greece > tel: +30-10-8981112 > fax: +30-10-8981877 > email: achill@matrix.gatewaynet.com > mantzios@softlab.ece.ntua.gr > > > ---------------------------(end of broadcast)--------------------------- > TIP 6: Have you searched our list archives? > > http://archives.postgresql.org > Regards, Oleg _____________________________________________________________ Oleg Bartunov, sci.researcher, hostmaster of AstroNet, Sternberg Astronomical Institute, Moscow University (Russia) Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/ phone: +007(095)939-16-83, +007(095)939-23-83
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~row4row6 | 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