On Mon, Mar 05, 2007 at 09:04:46PM -0600, Jim Nasby wrote: > FWIW, this sounds like a subset of the Query By Example stuff that > someone is working on. I don't have a URL handy since I'm on a plane, > but I think google can find it.
It's now called ObelisQ <http://pgfoundry.org/projects/qbe> Cheers, D > > On Mar 3, 2007, at 8:12 AM, ranbeer makin wrote: > > > > >Here is a description of what the SKYLINE operator is: > >--- > >Suppose you wish to purchase books and you are looking for books > >with high rating and low price. However, both the criteria of > >selecting books are complementary since books of higher rating are > >generally more expensive. For finding such books, you'll query the > >database system of the book store which will return a set of > >interesting books. The word 'interesting' implies all the books > >which are as good or better in both the dimensions (rating and > >price) and better in at least one dimension. This set of > >interesting points forms the Skyline. > >Skyline operator finds points which are not dominated by other data > >points. A point dominates another point if it is as good or better > >in all dimensions and better in at least one dimension. > > > >For specifying the Skyline queries, we extend SQL SELECT statement > >by an optional SKYLINE OF clause as given below: > > > >SELECT ... FROM ... WHERE... > > > >GROUP BY ... HAVING... > > > >SKYLINE OF [DISTINCT] d1 [MIN | MAX | DIFF], .., dm [MIN | MAX | > >DIFF] > > > >ORDER BY... > > > > > >Where, d1, d2 , , dm denote the dimensions of the Skyline, and MIN, > >MAX, DIFF specify whether the value in that dimension should be > >minimized, maximized, or simply be different. When DIFF is > >specified, two tuples are compared only if the value of the > >attribute on which DIFF is applied is different. > > > >When DISTINCT clause is specified and if there are two or more > >tuples with the same values of skyline attributes, then only one of > >them is retained in the skyline set. Otherwise, all of them are > >retained. > > > >Let's consider the above example of purchasing books with high > >rating and low price. > > > > > >Book Name > > > >Rating (out of 5) > > > >Price (Rs) > > > >Prodigal Daughter > > > >3 > > > >250 > > > >The city of Joy > > > >5 > > > >400 > > > >Vanishing Acts > > > >2 > > > >250 > > > >The Notebook > > > >4 > > > >300 > > > >Fountain Head > > > >5 > > > >350 > > > >Dear John > > > >5 > > > >500 > > > >Table1. Sample of book database > > > > > >Now, in order to get books with high rating and low price, you > >simply can issue the following query: > > > >SELECT * > > > >FROM Books > > > >SKYLINE OF rating MAX, price MIN; > > > > > >The Skyline set returned will be: > > > > > >Book Name > > > >Rating (out of 5) > > > >Price (Rs) > > > >Prodigal Daughter > > > >3 > > > >250 > > > >The Notebook > > > >4 > > > >300 > > > >Fountain Head > > > >5 > > > >350 > > > >Table2. Skyline set > > > > > >From this set, you can now make your choice of books, by weighing > >your personal preferences for price and rating of the books. > > > >For more information, you can refer to: > >S. Borzsonyi, D. Kossmann, and K. Stocker. The skyline operator. In > >ICDE, pages 421.430, 2001 > > > >--- > > > >Thanks. > > > > > > > >On 3/3/07, Martijn van Oosterhout <kleptog@svana.org> wrote: On > >Sat, Mar 03, 2007 at 07:02:41PM +0530, ranbeer makin wrote: > >> We at International Institute of Information Technology (IIIT) > >Hyderabad, > >> India, have extended the Postgres database > >> system with the skyline operation. For this work, we were guided > >by our > >> Prof. Kamalakar Karlapalem > >> (http://www.iiit.ac.in/~kamal/). > > > ><snip> > > > >> Can this piece of work contribute to PostgreSQL? If yes, then > >we'll send out > >> a detailed report of this project including changes > >> made, issues involved/need to be solved, limitations, future > >work, and the > >> source code etc. > > > >Well, that kind of depends. I have no idea what "Skyline" means so > >telling us what it is would be a good start > > > >Have a nice day, > >-- > >Martijn van Oosterhout <kleptog@svana.org> http://svana.org/ > >kleptog/ > >> From each according to his ability. To each according to his > >ability to litigate. > > > >-----BEGIN PGP SIGNATURE----- > >Version: GnuPG v1.4.1 (GNU/Linux) > > > >iD8DBQFF6XrkIB7bNG8LQkwRAqw8AJ0UKAy41OMxdgLUdY1G+e7R6/jGPwCZAQY4 > >9uCKFUW65UBIx7fpogR75Yo= > >=6Yc0 > >-----END PGP SIGNATURE----- > > > > > > -- > Jim Nasby [EMAIL PROTECTED] > EnterpriseDB http://enterprisedb.com 512.569.9461 (cell) > > > > ---------------------------(end of broadcast)--------------------------- > TIP 1: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to [EMAIL PROTECTED] so that your > message can get through to the mailing list cleanly -- David Fetter <[EMAIL PROTECTED]> http://fetter.org/ phone: +1 415 235 3778 AIM: dfetter666 Skype: davidfetter Remember to vote! Consider donating to PostgreSQL: http://www.postgresql.org/about/donate ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
