PRIMARY KEY and UNIQUE

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:

--- 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

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Andrew,

I thought that just by declaring the field the Primary Key makes it
automatically NOT NULL and UNIQUE?
Am I wrong?

Liam

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

__________________________________________________
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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... :-)

--
Porqu� usar una base de datos relacional cualquiera,
si pod�s usar PostgreSQL?
-----------------------------------------------------------------
Mart�n Marqu�s | mmarques@unl.edu.ar
Programador, Administrador, DBA | Centro de Telematica
Universidad Nacional
del Litoral
-----------------------------------------------------------------

On Vie 15 Feb 2002 08:42, Mart�n Marqu�s 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... ;-)

--
Porqu� usar una base de datos relacional cualquiera,
si pod�s usar PostgreSQL?
-----------------------------------------------------------------
Mart�n Marqu�s | mmarques@unl.edu.ar
Programador, Administrador, DBA | Centro de Telematica
Universidad Nacional
del Litoral
-----------------------------------------------------------------