[Dbix-class] Newbie - database structure

[Dermot]

On 22/02/2008, Zbigniew Lukasiak <zzbbyy at gmail.com> wrote:
>
> On Fri, Feb 22, 2008 at 4:26 PM, Dermot <paikkos at googlemail.com> wrote:
> >
> > > >There is a section about making 3 tables with SQLite3; books, authors
> and
> > > book_authors. The last table is described as
> > > >'book_authors' is a many-to-many join table between books & authors'
> > > >
> > > >My query is: Is this the "best practise" or an over-simplification
> for us
> > > newbies? Would you normally create a table for >joins to show many to
> many
> > > relationships? I would have though that you could use SQL statements
> to
> > > retreive that rather >than create a table of it.
> > >
> > >
> > > To answer your question, yes, you need a join table. Each record in it
> > > expresses a relationship between a record in table A and a record in
> table
> > > B.
> > >
> > > I'd recommend working through an SQL book that explains SQL concepts
> in
> > more
> > > detail as that really is a prerequisite for using a database or DBIC
> > > effectively.
> > > E.g. http://tinyurl.com/ywdxfu
> > >
> > >
> > I am unsettled by this. I went and re-read chapter 4 of the book I do
> have
> > (learning MYSQL) on database design and modelling. I still can't see the
> > value in creating a separate table for a join.
> >
> > If you have a 1:N table of authors and a table of books with the author
> ID
> > as a foreign key, surely that all you need to create any join you might
> > want. I know sqlite3 doesn't understand foreign keys but DBIC can create
> > them for you. Isn't that where the relationship is established?
>
>
> The standard technique with a joining table is for the case when you
> can have multiple authors on the book (hence the name many to many) -
> you cannot store all of them in one field.  If all you need is a 1:N
> relationship then you are ok without the linking table.


Is this "joining table" different from a SQL VIEW?
Dp.
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