Compact db design a bad idea?


#1

Hi,

I have tried two db designs and both can work but I wonder which one
the Rails Gurus would go with. This is a general db design question
that has cropped up in a few situation. Here is the example I’ve been
working on.

In an online store, categories has_and_belongs_to_many images and
products has_and_belongs_to_many images. The db has the basic three
tables

categories

  • id
  • name

products

  • id
  • name

images

  • id
  • filename

What I can’t decide on is how to do the join tables.

Option 1 - would have many join tables and require many join models.
(The join models are to use the position field for acts_as_list to
order the images)

categories_images

  • category_id
  • image_id

images_products

  • product_id
    _ image_id

Option 2 - have a one generic join table and only one join model

image_joins

  • owner_class
  • owner_id
  • image_id

In option 2 a record could be (Category, 2, 3) or (Product, 4, 1)


Option 1 seems simpler but could lead to some repetitive code (at
least in the data base definition).

Option 2 is a little more complicated and I don’t know how it fits
into the normalization stuff.

How do I choose?

Thanks,
Peter