Subject: Re: My first database assignment: Part II



>*Sigh* I know that futzing up on that many-to-many will count not as one
>error in programming, but three mistakes, since to fix the problem I had to
>delete a field, add another field, and change a relationship.


additional tip.. and i'll keep this one short this time.  ;-)

many-to-many relationships are an absolute pain in the patookus
to keep under control.   avoid them wherever possible.   the
good news is that you can model many-to-many relationships by
slapping a single relationship entity in the middle, and putting
many-to-one relationships on both sides:


nightmare:

    [ type 1 ]--\   /--[ type 2 ]
                 \ /
    [ type 1 ]----+----[ type 2 ]
                 / \
    [ type 1 ]--/   \--[ type 2 ]


merely complex:

    [ type 1 ]--+                   +--[ type 2 ]
                |                   |
    [ type 1 ]--+--[ association ]--+--[ type 2 ]
                |                   |
    [ type 1 ]--+                   +--[ type 2 ]