103 lines
4.4 KiB
Text
103 lines
4.4 KiB
Text
|
From ronz@ravensfield.com Tue May 22 17:35:37 2001
|
|||
|
|
Return-path: <ronz@ravensfield.com>
|
|||
|
|
Received: from carp.ravensfield.com ([209.41.227.126])
|
|||
|
|
by candle.pha.pa.us (8.10.1/8.10.1) with ESMTP id f4MLZaQ17913
|
|||
|
|
for <pgman@candle.pha.pa.us>; Tue, 22 May 2001 17:35:37 -0400 (EDT)
|
|||
|
|
Received: from coho.ravensfield.com (coho [209.41.227.117])
|
|||
|
|
by carp.ravensfield.com (Postfix) with SMTP
|
|||
|
|
id 5C2A9800D; Tue, 22 May 2001 16:46:38 -0500 (EST)
|
|||
|
|
Content-Type: text/plain;
|
|||
|
|
charset="iso-8859-1"
|
|||
|
|
From: Andrew Rawnsley <ronz@ravensfield.com>
|
|||
|
|
Organization: Ravensfield Geographic
|
|||
|
|
To: Bruce Momjian <pgman@candle.pha.pa.us>
|
|||
|
|
Subject: Re: [GENERAL] Queries across multiple databases (was: SELECT from a table in another database).
|
|||
|
|
Date: Tue, 22 May 2001 17:37:25 -0400
|
|||
|
|
X-Mailer: KMail [version 1.2]
|
|||
|
|
cc: Tom Lane <tgl@sss.pgh.pa.us>
|
|||
|
|
References: <200105220437.f4M4bUA00539@candle.pha.pa.us>
|
|||
|
|
In-Reply-To: <200105220437.f4M4bUA00539@candle.pha.pa.us>
|
|||
|
|
MIME-Version: 1.0
|
|||
|
|
Message-ID: <01052217372504.01367@coho.ravensfield.com>
|
|||
|
|
Content-Transfer-Encoding: 8bit
|
|||
|
|
Status: ORr
|
|||
|
|
|
|||
|
|
On Tuesday 22 May 2001 12:37am, Bruce Momjian wrote:
|
|||
|
|
> Can you send me a little sample of SCHEMA use?
|
|||
|
|
|
|||
|
|
Pardon if this is more long-winded or tangental than you are looking for...
|
|||
|
|
|
|||
|
|
What may beconfusing many people (not excluding myself from time to time) is
|
|||
|
|
that cross-schema queries may have nothing to do with cross-database queries,
|
|||
|
|
which is an entirely different kettle of trout.... SCHEMAs as used by at
|
|||
|
|
least by Oracle and Sybase are nothing more than users/object owners (I have
|
|||
|
|
no experience with DB2 or Informix, or anything more exotic than that).
|
|||
|
|
|
|||
|
|
Just off the top of my head, what would satisfy most people would be to be
|
|||
|
|
able to refer to objects as OWNER.OBJECT, with owner being 'within' the
|
|||
|
|
database (i.e. DATABASE.OWNER.OBJECT, which is how Sybase does it. Oracle has
|
|||
|
|
no 'database' parallel like that). Whether you do it Oracle-fashion and use
|
|||
|
|
the term SCHEMA for owner pretty universally or Sybase fashion and just pay
|
|||
|
|
lip service to the word doesn't really matter (unless there is a standards
|
|||
|
|
compliance issue).
|
|||
|
|
|
|||
|
|
As to creating schemas...In Oracle you have to execute the CREATE SCHEMA
|
|||
|
|
AUTHORIZATION <user> while logged in as that user before you can add objects
|
|||
|
|
under that user's ownership. While it seems trivial, if you have a situation
|
|||
|
|
where you do not want to grant a user session rights, you have to grant them
|
|||
|
|
session rights, log in as them, execute CREATE SCHEMA..., then revoke the
|
|||
|
|
session rights. Bah. A table created by user X in schema Y is also owned by
|
|||
|
|
user Y, and its user Y that has to have many of the object rights to create
|
|||
|
|
that table.
|
|||
|
|
|
|||
|
|
In Sybase, its essentially the same except the only real use for the CREATE
|
|||
|
|
SCHEMA command is for compliance and to group some DDL commands together.
|
|||
|
|
Other than that, Sybase always refers to schemas as owners. You don't have to
|
|||
|
|
execute CREATE SCHEMA... to create objects - you just need the rights. I've
|
|||
|
|
never used it at least - the only thing I see in it is eliminating the need
|
|||
|
|
to type 'go' after every DDL command.
|
|||
|
|
|
|||
|
|
As for examples from Oracle space -
|
|||
|
|
|
|||
|
|
Here is a foreign key reference with delete triggers from a table in
|
|||
|
|
schema/user PROJECT to tables in schemas/users SERVICES and WEBCAL:
|
|||
|
|
|
|||
|
|
CREATE TABLE PROJECT.tasks_users (
|
|||
|
|
<EFBFBD> <20>event_id INTEGER REFERENCES WEBCAL.tasks(event_id) ON DELETE CASCADE,
|
|||
|
|
<EFBFBD> <20>user_id VARCHAR2(25) REFERENCES SERVICES.users(user_id) ON DELETE CASCADE,
|
|||
|
|
<EFBFBD> <20>confirmed CHAR(1),
|
|||
|
|
<EFBFBD> <20>PRIMARY KEY (event_id,user_id)
|
|||
|
|
);
|
|||
|
|
|
|||
|
|
A join between tables in would be
|
|||
|
|
SELECT <20> A.SAMPLE_ID,
|
|||
|
|
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> A.CONCENTRATION,
|
|||
|
|
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> A.CASNO,
|
|||
|
|
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> B.PARAMETER,
|
|||
|
|
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> C.DESCRIPTION AS STYPE
|
|||
|
|
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> FROM HAI.RESULTS A, SAMPLETRACK.PARAMETERS B,
|
|||
|
|
SAMPLETRACK.SAMPLE_TYPE C
|
|||
|
|
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> WHERE A.CASNO = B.CASNO AND A.SAMPLE_TYPE = B.SAMPLE_TYPE
|
|||
|
|
|
|||
|
|
In both Oracle and Sybase, all the objects are in the same 'database'
|
|||
|
|
(instance in Oracle), as I assume they would be in Postgres. There is I
|
|||
|
|
assume a name space issue - one should be able to create a FOO.BAR and a
|
|||
|
|
BAR.BAR in the same database.
|
|||
|
|
|
|||
|
|
> I may be adding it to
|
|||
|
|
> 7.2 inside the same code that maps temp table names to real tables.
|
|||
|
|
>
|
|||
|
|
|
|||
|
|
Excellent! I see light at the end of the tunnel (I will say the Postgres
|
|||
|
|
maintainers are among the most solidly competent around - one never has any
|
|||
|
|
real doubts about the system's progress).
|
|||
|
|
|
|||
|
|
--
|
|||
|
|
Regards,
|
|||
|
|
|
|||
|
|
Andrew Rawnsley
|
|||
|
|
Ravensfield Digital Resource Group, Ltd.
|
|||
|
|
(740) 587-0114
|
|||
|
|
www.ravensfield.com
|
|||
|
|
|