On 5 Dec 2002 at 12:09, Christopher Kings-Lynne wrote:
> > > Isn't it identical? The CONSTRAINT <const> is SQL standard optional
> clause
> > > for all commands that add constraints.
> >
> > Except that one is ADD CONSTRAINT, the other is an ADD FOREIGN KEY.
> > They are similar in nature but different overall.
>
> I think you're getting a little confused here, Dan.
>
> http://www3.us.postgresql.org/users-lounge/docs/7.3/postgres/sql-altertable.
> html
>
> There is only one command for adding constraints to a table. It has this
> syntax:
>
> ALTER TABLE [ ONLY ] table [ * ]
> ADD table_constraint
>
> The table_constraint clause is defined like this (basically):
>
> [CONSTRAINT blah] (PRIMARY KEY or UNIQUE or FOREIGN KEY) ...
>
> So, the CONSTRAINT blah clause allows you to specify a name for any of the 3
> types of constraint: primary key, unique or foreign key. There's nothing
> special about foreign keys in this case.
>
> If you don't put in the CONSTRAINT blah clause, you get an automatically
> assigned constraint name.
Regardless of what is documented, the following is valid and works:
ALTER TABLE slave ADD FOREIGN KEY (master_id) REFERENCES master (id) ON DELETE CASCADE;
--
Dan Langille : http://www.langille.org/
