On Wed, 27 Feb 2008, Dermot wrote:
On 22/02/2008, Zbigniew Lukasiak <[EMAIL PROTECTED]> wrote:
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.
Is this "joining table" different from a SQL VIEW?
Err, no, not in the slightest, how did you get that impression? A view is
just a query represented like a table so you dont have to repeat writing
the query all the time (plus some bonus of the database knowing it up
front so it can optimise.)
Can you describe how you came to this question? I'm really confused as to
how one can confuse "joining table" with "view".
Jess
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