title: In rails, how to destroy a 'join table item' with out deleting the real record?
body: <p>I get confuse now, I don't know how to delete/destroy a record in a join table:</p>
  
  <hr>
  
  <pre><code>class Task &lt; ActiveRecord::Base
    belongs_to :schema
    belongs_to :to_do
  end
  
  class Todo &lt; ActiveRecord::Base
    belongs_to :schema
    has_many :tasks
  end
  
  class Schema &lt; ActiveRecord::Base
    has_many :todos
    has_many :tasks, :through =&gt; :todos
  end
  </code></pre>
  
  <hr>
  
  <pre><code>&gt;&gt; sc = Schema.new
  &gt;&gt; sc.tasks &lt;&lt; Task.new
  &gt;&gt; sc.tasks &lt;&lt; Task.new
  &gt;&gt; sc.tasks &lt;&lt; Task.new
  ...
  &gt;&gt; sc.tasks.delete(Task.first) # I just want to delete/destroy the join item here.
  # But that deleted/destroyed the Task.first.
  </code></pre>
  
  <hr>
  
  <p>What can I do if I just want to destroy the relation item?</p>