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* [NOVICE] Primary and Foreign Key?
@ 1970-01-01 00:00
0 siblings, 0 replies; 6+ messages in thread
From: @ 1970-01-01 00:00 UTC (permalink / raw)
To: pgsql-novice
I have the following related tables:
PEOPLE
--------------
peopleid pkey,
name,
etc
GROUPS
-------------
groupid pkey,
description,
etc
PEOPLEGROUPS
-------------------
peopleid pkey/fkey,
groupid pkey/fkey
What is the CORRECT way (in Postgres) to define the PEOPLEGROUPS table so
that it has both the double primary key AND still acts as a foreign key for
people.peopleid and groups.groupid? Can i specify both or is this not
necessary? Any suggestions would be appreciated.
Thanks!
^ permalink raw reply [nested|flat] 6+ messages in thread
* [NOVICE] Primary and Foreign Key?
@ 1970-01-01 00:00
0 siblings, 0 replies; 6+ messages in thread
From: @ 1970-01-01 00:00 UTC (permalink / raw)
To: pgsql-novice
I have the following related tables:
PEOPLE
--------------
peopleid pkey,
name,
etc
GROUPS
-------------
groupid pkey,
description,
etc
PEOPLEGROUPS
-------------------
peopleid pkey/fkey,
groupid pkey/fkey
What is the CORRECT way (in Postgres) to define the PEOPLEGROUPS table so
that it has both the double primary key AND still acts as a foreign key for
people.peopleid and groups.groupid? Can i specify both or is this not
necessary? Any suggestions would be appreciated.
Thanks!
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^ permalink raw reply [nested|flat] 6+ messages in thread
* Primary and Foreign Key?
@ 2005-09-22 00:46 A. Banks <abanks@insightbb.com>
0 siblings, 2 replies; 6+ messages in thread
From: A. Banks @ 2005-09-22 00:46 UTC (permalink / raw)
To: pgsql-novice
I have the following related tables:
PEOPLE
--------------
peopleid pkey,
name,
etc
GROUPS
-------------
groupid pkey,
description,
etc
PEOPLEGROUPS
-------------------
peopleid pkey/fkey,
groupid pkey/fkey
What is the CORRECT way (in Postgres) to define the PEOPLEGROUPS table so
that it has both the double primary key AND still acts as a foreign key for
people.peopleid and groups.groupid? Can i specify both or is this not
necessary? Any suggestions would be appreciated.
Thanks!
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.344 / Virus Database: 267.11.3/107 - Release Date: 9/20/2005
^ permalink raw reply [nested|flat] 6+ messages in thread
* Re: Primary and Foreign Key?
@ 2005-09-24 06:45 Wayne Unruh <waynepunruh@hotmail.com>
parent: A. Banks <abanks@insightbb.com>
1 sibling, 0 replies; 6+ messages in thread
From: Wayne Unruh @ 2005-09-24 06:45 UTC (permalink / raw)
To: abanks@insightbb.com; pgsql-novice
In relational databases A table can have at most one primary key. However,
you are not required to have a primary key, so I would just have the two
foreign keys in the table PEOPLEGROUPS.
For more information on Constraints see
http://www.postgresql.org/docs/8.0/interactive/ddl-constraints.html
Wayne Unruh
^ permalink raw reply [nested|flat] 6+ messages in thread
* Re: Primary and Foreign Key?
@ 2005-09-24 11:31 Oliver Elphick <olly@lfix.co.uk>
parent: A. Banks <abanks@insightbb.com>
1 sibling, 0 replies; 6+ messages in thread
From: Oliver Elphick @ 2005-09-24 11:31 UTC (permalink / raw)
To: A. Banks <abanks@insightbb.com>; +Cc: pgsql-novice
On Wed, 2005-09-21 at 19:46 -0500, A. Banks wrote:
> I have the following related tables:
>
> PEOPLE
> --------------
> peopleid pkey,
> name,
> etc
>
>
> GROUPS
> -------------
> groupid pkey,
> description,
> etc
>
>
> PEOPLEGROUPS
> -------------------
> peopleid pkey/fkey,
> groupid pkey/fkey
>
>
> What is the CORRECT way (in Postgres) to define the PEOPLEGROUPS table so
> that it has both the double primary key AND still acts as a foreign key for
> people.peopleid and groups.groupid? Can i specify both or is this not
> necessary? Any suggestions would be appreciated.
Your terminology is a bit wrong; there can only ever be one primary key
for a table; what you want is probably a single primary key made up of
two columns.
Your definition will look like this:
CREATE TABLE people (
peopleid SERIAL PRIMARY KEY, -- SERIAL is an INTEGER that autoincrements
-- if no value is supplied on insertion
name TEXT NOT NULL,
...
);
CREATE TABLE groups (
groupid SERIAL PRIMARY KEY,
name TEXT NOT NULL,
...
);
CREATE TABLE peoplegroups (
peopleid INTEGER
REFERENCES people (peopleid)
ON UPDATE CASCADE ON DELETE NO ACTION,
groupid INTEGER
REFERENCES people (peopleid)
ON UPDATE CASCADE ON DELETE NO ACTION,
PRIMARY KEY (peopleid, groupid)
);
--
Oliver Elphick olly@lfix.co.uk
Isle of Wight http://www.lfix.co.uk/oliver
GPG: 1024D/A54310EA 92C8 39E7 280E 3631 3F0E 1EC0 5664 7A2F A543 10EA
========================================
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^ permalink raw reply [nested|flat] 6+ messages in thread
* Re: Primary and Foreign Key?
@ 2005-09-24 14:55 Announce <truthhurts@insightbb.com>
0 siblings, 0 replies; 6+ messages in thread
From: Announce @ 2005-09-24 14:55 UTC (permalink / raw)
To: pgsql-novice
I think i found what i was looking for in the docs:
5.3.4. Primary Keys
Technically, a primary key constraint is simply a combination of a unique
constraint and a not-null constraint.
So i suppose i suppose i would use PRIKARY KEY(peopleid,groupid) to enforce
the UNIQUE NOT NULL constraint in one expression.
Thanks!
-----Original Message-----
From: Wayne Unruh [mailto:waynepunruh@hotmail.com]
Sent: Saturday, September 24, 2005 1:46 AM
To: abanks@insightbb.com; pgsql-novice@postgresql.org
Subject: RE: [NOVICE] Primary and Foreign Key?
In relational databases A table can have at most one primary key. However,
you are not required to have a primary key, so I would just have the two
foreign keys in the table PEOPLEGROUPS.
For more information on Constraints see
http://www.postgresql.org/docs/8.0/interactive/ddl-constraints.html
Wayne Unruh
^ permalink raw reply [nested|flat] 6+ messages in thread
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1970-01-01 00:00 [NOVICE] Primary and Foreign Key?
1970-01-01 00:00 [NOVICE] Primary and Foreign Key?
2005-09-22 00:46 Primary and Foreign Key? A. Banks <abanks@insightbb.com>
2005-09-24 06:45 ` Wayne Unruh <waynepunruh@hotmail.com>
2005-09-24 11:31 ` Oliver Elphick <olly@lfix.co.uk>
2005-09-24 14:55 Re: Primary and Foreign Key? Announce <truthhurts@insightbb.com>
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