Hello, and a good day to you. I am new to MYSQL, and was wondering how
I go about creating tables using foreign keys.

My question is, I create a table called carrier.

+------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+----------------+
| carrier_id | int(4) | NO | PRI | NULL | auto_increment |
| name | varchar(30) | NO | | NULL | |
+------------+-------------+------+-----+---------+----------------+

I would like to make another table called booking to include the carrier_id.

When I create the booing table, do I just specify FOREIGN KEY
(carrier_id), and use the same attributes
carrier_id int(4) not null?

Thanks,

Bob
--

A man without an answer
Is like a bird with broken wings
wrapped up in its misery
forgetting how to sing

Bob De Mars wrote:
> Hello, and a good day to you. I am new to MYSQL, and was wondering
> how I go about creating tables using foreign keys.
When I am new to something, I read the manual. I find it saves me having to
wonder about things like this.

> When I create the booing table, do I just specify FOREIGN KEY
> (carrier_id), and use the same attributes
> carrier_id int(4) not null?
No, you have to follow the instructions in the manual. In general in
programming, you will find that it is not possible to just make up your own
syntax on a whim. You will find this section coinsidentally called FOREIGN
KEY Constraints useful:
http://dev.mysql.com/doc/refman/5.0/...nstraints.html

>
> Thanks,
>
> Bob
You're welcome.

On Fri, 30 May 2008 20:20:19 +0200, Bob De Mars <bob@grunners.com_nospam>
wrote:

> Hello, and a good day to you. I am new to MYSQL, and was wondering how
> I go about creating tables using foreign keys.
>
> My question is, I create a table called carrier.
>
> +------------+-------------+------+-----+---------+----------------+
> | Field | Type | Null | Key | Default | Extra |
> +------------+-------------+------+-----+---------+----------------+
> | carrier_id | int(4) | NO | PRI | NULL | auto_increment |
> | name | varchar(30) | NO | | NULL | |
> +------------+-------------+------+-----+---------+----------------+
>
> I would like to make another table called booking to include the
> carrier_id.
>
> When I create the booing table, do I just specify FOREIGN KEY
> (carrier_id), and use the same attributes
> carrier_id int(4) not null?

Read the manual regarding Foreign Keys, especially the syntax, and keep 2
important things in mind:
- Not all engines will support foreign keys, for instance MyISAM doesn't,
InnoDB does, however, when setting a Foreign Key constraint on a table
which' engine doesn't support it, MySQL will not complain, allthough your
constraint that just appeared to be set will do absolutely nothing.
- The columns in a constraint have to be of the exact same type, which
could include character set & collation, however, a column can be defined
as NULL while the column referenced is NOT NULL, creating the possiblity
to add record not bound by the constraint. Of course, only use that if
that's what you want.

And a warning: MySQL's error messages about failing settings constraints
are incredibly cryptic and almost never helpfull. Basically, if creating a
constraint fails check & recheck the columns you'd like to match, a SHOW
FULL COLUMNS FORM tablename can give you some extra insight in those.
--
Rik Wasmus
....spamrun finished