From: | "Gurjeet Singh" <singh(dot)gurjeet(at)gmail(dot)com> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, "Pgsql Hackers" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Creating a Pseudocolumn |
Date: | 2006-05-16 09:48:19 |
Message-ID: | 65937bea0605160248r6ddc8064q572f4268e9f571f8@mail.gmail.com |
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Lists: | pgsql-hackers |
I think Jonah is referring to the the 'START WITH ... CONNECT BY'
clause feature from Oracle. Am I right Jonah?
For such queries, Oracle introduces a pseudocolumn LEVEL, that
holds the value of the indentation level of the current rusultant row.
In Oracle, the LEVEL column returns 0 for the root node of a
hierarchy, 1 for it's children, 2 for their children, and so forth.
LEVEL is commonly used to indent hierarchical results.
LEVEL might not be a part of the standard, but it is very handy
when dealing with hierarchical queries.
The chapter 1 (http://www.oreilly.com/catalog/sqlpr/chapter/ch01.pdf)
of book 'SQL Pocket Guide' elaborates more on it.
Gurjeet.
On 5/16/06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Perhaps you should start by explaining what the heck you're talking
> about ;-). I can find nothing in the SQL2003 spec that sounds anything
> like a LEVEL function or pseudocolumn.
>
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