On Fri, Feb 22, 2008 at 4:26 PM, Dermot <[EMAIL PROTECTED]> 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. Cheers, http://perlalchemy.blogspot.com/ _______________________________________________ List: http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/dbix-class IRC: irc.perl.org#dbix-class SVN: http://dev.catalyst.perl.org/repos/bast/DBIx-Class/ Searchable Archive: http://www.grokbase.com/group/[EMAIL PROTECTED]
