Does Datamapper for Codeigniter force an intermediate table for all relationships?

Question

I'm moving towards an ORM for my codeigniter application and have chosen datamapper. However, in the rules section, it states the following:

A joining table must exist between each related normal tables, regardless of the type of relationship.

I have dozens of tables that are in a one->many relationship. Does this mean that I have to create intermediate (joining) tables between each of them as if they were many-many?

Answer 1

Yes, unfortunately, it does mean that. This is one of the reasons why I had to change my DB design

Answer 2

No, actually, the model that has a $has_one relationship set will have a field ending in _id, which refers to the object with the $has_many relationship set.

So, for example:

class Recipe extends DataMapper {
    var $has_many = array('product', 'rating', 'recipe_category');
    var $has_one = array('recipe_source', 'user');
    (...)
}

class Recipe_Source extends DataMapper {
    var $has_many = array('recipe');
    (...)
}

In this case, DataMapper made a table recipes with a recipe_source_id column, and a recipe_sources table that required no extra fields.

Now, for many-to-many relationships, a join table will be created, and it follows a strict convention.

The join table name will be the two plurals of the joined models, separated by an underscore, in alphabetical order.

So, using this model:

class Product extends DataMapper {
    var $has_one = array('cheese_style', 'butter_style', 'cheese_flavor');
    var $has_many = array('product_size', 'recipe');
    (...)
}

Now, I end up with a join table in my database called products_recipes.

This is how it is handled by the DMZ DataMapper library (http://www.overzealous.com/dmz/), which is supposed to be a drop-in replacement for the old stensi DataMapper library, so I'm going to assume the conventions are the same.

Even so, I highly recommend making the switch to DMZ.