Thread: constrains questios ..

Hi,

is better to create constrains while creating table or after the table 
is created? I'm working on sql script which should create about 40 tables.


Best Regards,
Rafal

On Tuesday 11 February 2003 16:35, Rafal Kedziorski wrote:
Hi,

> is better to create constrains while creating table or after the table
> is created? I'm working on sql script which should create about 40 tables.

I usually first create the tables, then the constraints. Rational: You can
create the tables in any sequence you want to.

HTH

Johannes Lochmann

--
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> > is better to create constrains while creating table or after the
table
> > is created? I'm working on sql script which should create about 40
> tables.
> 
> I usually first create the tables, then the constraints. Rational: You
can
> create the tables in any sequence you want to.
> 
> HTH
> 
> Johannes Lochmann
> 

Can you please demonstrate the syntax you would use to create the
constraints?  I'm not real clear on this and my attempts haven't
produced what I wanted.

--
Matthew Nuzum
www.bearfruit.org
cobalt@bearfruit.org

On Tuesday 11 February 2003 18:41, Matthew Nuzum wrote:
> Can you please demonstrate the syntax you would use to create the
> constraints?  I'm not real clear on this and my attempts haven't
> produced what I wanted.

Checked the docs? They are really good at this point. Anyways.

The following creates Tables A, B and AB. A and B have an id and a text field,
AB connects them (N:M relation).

create table A (id integer not null primary key,something varchar(16)
);

create table B (id integer not null primary key,otherthing varchar(16)
);

create table AB (id_a integer not null,id_b integer not null,
constraint pk_AB primary key(id_a, id_b)
);

create unique index u_A_something on A (something);
create unique index u_A_otherthing on B (otherthing);

alter table AB add constraint fk_AB_A_exists foreign key(id_a) references
A(id);
alter table AB add constraint fk_AB_B_exists foreign key(id_b) references
B(id);

HTH

Johannes Lochmann

--
Disclaimer - These opiini^H^H damn! ^H^H ^Q ^[ .. :w :q :wq :wq! ^d X^?
exit X Q ^C ^c ^? :quitbye  CtrlAltDel  ~~q :~q logout save/quit :!QUIT
^[zz ^[ZZZZZZ ^H  man vi ^@ ^L ^[c ^# ^E ^X ^I ^T ? help helpquit ^D ^d
man help ^C exit ?Quit ?q CtrlShftDel "Hey, what does this button d..."