Databases
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    <p>You should not expect to be able to generate your app via scaffolding alone. It is meant only to provide an example for getting started.</p> <p>The most flexible kind of many-to-many relationship in rails is called <a href="http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association" rel="nofollow noreferrer">has many through</a>. This requires a join table which would typically be called 'categorisations' in this case. It would need a <code>product_id</code> column declared as <code>belongs to :product</code> and a <code>category_id</code> column declared as <code>belongs_to :category</code>. The three models (including the join model) would be declared thus:</p> <pre><code># Table name: products # Columns: # name:string class Product &lt; ActiveRecord::Base has_many :categorisations, dependent: :destroy has_many :categories, through: :categorisations end # Table name: categories # Columns: # name:string class Category &lt; ActiveRecord::Base has_many :categorisations, dependent: :destroy has_many :products, through: :categorisations end # Table name: categorisations # Columns: # product_id:integer # category_id:integer class Categorisation &lt; ActiveRecord::Base belongs_to :product belongs_to :category end </code></pre> <p>Note that I've named the columns <code>name</code> rather than <code>prd_name</code> since this is both human-readable and avoids redundant repetition of the table name. This is highly recommended when using rails.</p> <p>The models can be generated like this:</p> <pre><code>rails generate model product name rails generate model category name rails generate model categorisation product:references category:references </code></pre> <p>As for generating the scaffolding, you could replace <code>model</code> with <code>scaffold</code> in the first two commands. Again though, I don't recommend it except as a way to see an example to learn from.</p>
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    1. COwhat about the migration file?
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    2. COSee updated answer.
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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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