From: Martijn Tonies
Date: May 26 2005 7:12am
Subject: Re: InnoDB to MyISAM
List-Archive: http://lists.mysql.com/mysql/184626
Message-Id: <00d701c561c2$4172f610$3802a8c0@martijnws>
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit



> >> I think you're confusing referential constraints with foreign keys.
> >
> > In my book, referential constraints and foreign key constraints (the
full
> > name)
> > are the same.
>
> Yes, referential constraints and foreign key constraints are the same
thing.
> Notice the word constraints.
>
> Let me say this again:
>
> A foreign key is merely a column which references a primary key or a
unique
> key in the same or another table.
>
> A referential constraint (or foreign key constraint if you prefer) defines
> an integrity condition that must be satisfied by all the rows in two
tables.
>
> See the difference?  So yes, MyISAM has foreign keys, no MyISAM does not
> have foreign key constraints.  Kindly don't go around saying MyISAM
doesn't
> have foreign keys because it simply makes no sense.  Referential integrety
> is not required for foreign keys.  The only thing you need to have a
foreign
> key is a column which contains the value of a primary key or unique key in
> another table.

Right. We can agree on this wording if you like. I've never met it before
in such a way though :-)

Nevertheless, foreign key constraints belong in the database, not in your
application... If you have foreign keys (your wording), you need foreign
key constraints. Period. Plain and simple. No discussion :-)

With regards,

Martijn Tonies
Database Workbench - tool for InterBase, Firebird, MySQL, Oracle & MS SQL
Server
Upscene Productions
http://www.upscene.com