Обсуждение: PRIMARY KEY and UNIQUE
Hi, I have a such a table. CREATE TABLE int_article ( name VARCHAR(12) UNIQUE headline TEXT, summary TEXT, main TEXT, footer TEXT, PRIMARY KEY (name) ); Is the UNIQUE constraint neccessary, because if have specified the column name to be the primary key. Thanks in advance Erwin
If it is a primary key then it will automatically be UNIQUE. You do not need the unique next to the VARCHAR in this situation Darren On Thu, 14 Feb 2002, Erwin Ambrosch wrote: > Hi, > > I have a such a table. > > CREATE TABLE int_article ( > name VARCHAR(12) UNIQUE > headline TEXT, > summary TEXT, > main TEXT, > footer TEXT, > PRIMARY KEY (name) > ); > > Is the UNIQUE constraint neccessary, because if have specified the column > name to be the primary key. > > Thanks in advance > Erwin > > ---------------------------(end of broadcast)--------------------------- > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org >
--- Erwin Ambrosch <ambre@ebutec.com> wrote: > Hi, > > I have a such a table. > > CREATE TABLE int_article ( > name VARCHAR(12) UNIQUE > headline TEXT, > summary TEXT, > main TEXT, > footer TEXT, > PRIMARY KEY (name) > ); > > Is the UNIQUE constraint neccessary, because if have > specified the column > name to be the primary key. > > Thanks in advance > Erwin No; but if you eliminate 'UNIQUE', you'll need to replace it with 'NOT NULL'. Andrew Gould __________________________________________________ Do You Yahoo!? Send FREE Valentine eCards with Yahoo! Greetings! http://greetings.yahoo.com
Andrew, I thought that just by declaring the field the Primary Key makes it automatically NOT NULL and UNIQUE? Am I wrong? Liam >-----Original Message----- >From: pgsql-general-owner@postgresql.org >[mailto:pgsql-general-owner@postgresql.org]On Behalf Of Andrew Gould >Sent: Thursday, February 14, 2002 10:31 AM >To: ambre@ebutec.com; pgsql-general@postgresql.org >Subject: Re: [GENERAL] PRIMARY KEY and UNIQUE > > >--- Erwin Ambrosch <ambre@ebutec.com> wrote: >> Hi, >> >> I have a such a table. >> >> CREATE TABLE int_article ( >> name VARCHAR(12) UNIQUE >> headline TEXT, >> summary TEXT, >> main TEXT, >> footer TEXT, >> PRIMARY KEY (name) >> ); >> >> Is the UNIQUE constraint neccessary, because if have >> specified the column >> name to be the primary key. >> >> Thanks in advance >> Erwin > >No; but if you eliminate 'UNIQUE', you'll need to >replace it with 'NOT NULL'. > >Andrew Gould > > >__________________________________________________ >Do You Yahoo!? >Send FREE Valentine eCards with Yahoo! Greetings! >http://greetings.yahoo.com > >---------------------------(end of >broadcast)--------------------------- >TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to >majordomo@postgresql.org) >
I just tried it; and you are correct. I must be confusing my database applications. Andrew --- Liam DeMasi <ldemasi@acsinc-nj.com> wrote: > Andrew, > > I thought that just by declaring the field the > Primary Key makes it > automatically NOT NULL and UNIQUE? > Am I wrong? > > Liam > > >-----Original Message----- > >From: pgsql-general-owner@postgresql.org > >[mailto:pgsql-general-owner@postgresql.org]On > Behalf Of Andrew Gould > >Sent: Thursday, February 14, 2002 10:31 AM > >To: ambre@ebutec.com; pgsql-general@postgresql.org > >Subject: Re: [GENERAL] PRIMARY KEY and UNIQUE > > > > > >--- Erwin Ambrosch <ambre@ebutec.com> wrote: > >> Hi, > >> > >> I have a such a table. > >> > >> CREATE TABLE int_article ( > >> name VARCHAR(12) UNIQUE > >> headline TEXT, > >> summary TEXT, > >> main TEXT, > >> footer TEXT, > >> PRIMARY KEY (name) > >> ); > >> > >> Is the UNIQUE constraint neccessary, because if > have > >> specified the column > >> name to be the primary key. > >> > >> Thanks in advance > >> Erwin > > > >No; but if you eliminate 'UNIQUE', you'll need to > >replace it with 'NOT NULL'. > > > >Andrew Gould > > > > > >__________________________________________________ > >Do You Yahoo!? > >Send FREE Valentine eCards with Yahoo! Greetings! > >http://greetings.yahoo.com > > > >---------------------------(end of > >broadcast)--------------------------- > >TIP 2: you can get off all lists at once with the > unregister command > > (send "unregister YourEmailAddressHere" to > >majordomo@postgresql.org) > > > > > ---------------------------(end of > broadcast)--------------------------- > TIP 6: Have you searched our list archives? > > http://archives.postgresql.org __________________________________________________ Do You Yahoo!? Send FREE Valentine eCards with Yahoo! Greetings! http://greetings.yahoo.com
On Jue 14 Feb 2002 12:29, Darren Ferguson wrote:
> If it is a primary key then it will automatically be UNIQUE.
Even more, it will create a "INDEX UNIQUE ...." over the primary key field.
Saludos... :-)
--
Porqué usar una base de datos relacional cualquiera,
si podés usar PostgreSQL?
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Martín Marqués | mmarques@unl.edu.ar
Programador, Administrador, DBA | Centro de Telematica
Universidad Nacional
del Litoral
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On Vie 15 Feb 2002 08:42, Martín Marqués wrote:
> On Jue 14 Feb 2002 12:29, Darren Ferguson wrote:
> > If it is a primary key then it will automatically be UNIQUE.
>
> Even more, it will create a "INDEX UNIQUE ...." over the primary key field.
Sorry, I confussed PRIMARY KEY with SERIAL data type.
Ignore that about the INDEX.
Saludos... ;-)
--
Porqué usar una base de datos relacional cualquiera,
si podés usar PostgreSQL?
-----------------------------------------------------------------
Martín Marqués | mmarques@unl.edu.ar
Programador, Administrador, DBA | Centro de Telematica
Universidad Nacional
del Litoral
-----------------------------------------------------------------