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Thread: PRIMARY KEY and INDEX

PRIMARY KEY and INDEX

From
"Nosyman"
Date:
It is necessary to define an index for a primary key column?

Let's have an example
CREATE TABLE users(
id_user INTEGER PRIMARY KEY,
user_name VARCHAR(25)
);

Does PgSQL automatically create an index for id_user (primary key) or it
must be created by hand?

Thanks


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Re: PRIMARY KEY and INDEX

From
Achilleus Mantzios
Date:
O kyrios Nosyman egrapse stis Sep 2, 2004 :

> It is necessary to define an index for a primary key column?
> 
> Let's have an example
> CREATE TABLE users(
> id_user INTEGER PRIMARY KEY,
> user_name VARCHAR(25)
> );
> 
> Does PgSQL automatically create an index for id_user (primary key) or it
> must be created by hand?

Yes a unique index is created automatically so as to enforce the 
PK constraint.

> 
> Thanks
> 
> 
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-- 
-Achilleus

Re: PRIMARY KEY and INDEX

From
Devrim GUNDUZ
Date:
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Hi,

On Thu, 2 Sep 2004, Nosyman wrote:

> It is necessary to define an index for a primary key column?
>
> Let's have an example
> CREATE TABLE users(
> id_user INTEGER PRIMARY KEY,
> user_name VARCHAR(25)
> );
>
> Does PgSQL automatically create an index for id_user (primary key) or it
> must be created by hand?

You could give it a try before asking:

test=# CREATE TABLE users(
test(# id_user INTEGER PRIMARY KEY,
test(# user_name VARCHAR(25)
test(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index 
"users_pkey" for table "users"
CREATE TABLE

Regards,
- --
Devrim GUNDUZ 
devrim~gunduz.org                devrim.gunduz~linux.org.tr            http://www.tdmsoft.com
http://www.gunduz.org
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