Обсуждение: Don't understand creation statement's answer

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Don't understand creation statement's answer

От
Thomas SMETS
Дата:
Hi,

In the long term I'm willing to construct a Little Java application that
runs a library. I was looking to create a few table & connect them
according to a non existing model . To create the Author table here's
what I thought doing for a table that should only contain The Name & the
Surname of the Author (once per Author).


<snip>
tsmets=> create sequence author_seq;
CREATE  

tsmets=> create table author ( 
tsmets=>     author_id numeric primary key default
nextval('author_seq'),  
tsmets=>     name char(25) not null, 
tsmets=>     surname char(25) not null
tsmets=>     );
NOTICE:  CREATE TABLE/PRIMARY KEY will create implicit index
'author_pkey' for table 'author'
CREATE
tsmets=> \d author                             Table "author"Attribute |     Type      |                   Modifier
-----------+---------------+----------------------------------------------author_id | numeric(30,6) | not null default
nextval('author_seq'::text)name      | char(25)      | not nullsurname   | char(25)      | not null
Index: author_pkey
tsmets=>                       
</snip>

Now the question is :
What is the meaning of the following statement in the table description
?
Attribute |     Type      |                   Modifier
-----------+---------------+----------------------------------------------author_id | numeric(30,6) | not null default
nextval('author_seq'::text)

Why was my author_id changesdin a "nextval('author_seq'::text)".
There's no text here ?

That for highlighting the meaning of this ?

Thomas,



-- 
Sun Dec 17 19:42:31 CET 2000

Thomas SMETS                        e-mail : tsmets@altern.org
Av. de la Brabançonne 133 / 3       Tel. : +32 (0)2 742. 05. 94.
1030 Bruxelles
======= Quote of the Day =========
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Re: Don't understand creation statement's answer

От
Mathijs Brands
Дата:
On Mon, Dec 18, 2000 at 12:32:54AM +0100, Thomas SMETS allegedly wrote:
> tsmets=> create sequence author_seq;
> CREATE  
> 
> tsmets=> create table author ( 
> tsmets=>     author_id numeric primary key default
> nextval('author_seq'),  
> tsmets=>     name char(25) not null, 
> tsmets=>     surname char(25) not null
> tsmets=>     );
> NOTICE:  CREATE TABLE/PRIMARY KEY will create implicit index
> 'author_pkey' for table 'author'

> Now the question is :
> What is the meaning of the following statement in the table description
> ?
> 
>  Attribute |     Type      |                   Modifier
> -----------+---------------+----------------------------------------------
>  author_id | numeric(30,6) | not null default
> nextval('author_seq'::text)
> 
> Why was my author_id changesdin a "nextval('author_seq'::text)".
> There's no text here ?

nextval takes one parameter of the type text. It's just an explicit typecast.
The output of nextval is a number, as you requested.

I hope this helps,

Mathijs
-- 
"Books constitute capital."     Thomas Jefferson

Re: Don't understand creation statement's answer

От
Christopher Sawtell
Дата:
On Mon, 18 Dec 2000 12:32, Thomas SMETS wrote:
> Hi,
>
> In the long term I'm willing to construct a Little Java application that
> runs a library.

you might find http://www.koha.org interesting

Library management on all free software.

-- 
Sincerely etc.,
NAME       Christopher SawtellCELL PHONE 021 257 4451ICQ UIN    45863470EMAIL      csawtell @ xtra . co . nzCNOTES
ftp://ftp.funet.fi/pub/languages/C/tutorials/sawtell_C.tar.gz
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