title: Delete all entries in a MxN relation with non-null FK constraints
body: <p>I have two entities A and B that are related in a MxN relation through an intermediary table, thus making a total of three tables. My relation table R has non-nullable FK constraints on the other two tables.</p>
  
  <p>I want to delete all entries from tables A and B and R where A obeys some constraint (I can supply the ids in A table for instance).</p>
  
  <p>Is it possible to delete entries from the three tables without resorting to a stored procedure and without violating the non-null constraint?</p>
  
  <p>I want something like:</p>
  
  <pre><code>delete from A a, B b, R r where a.id=r.fk_a and B.id=r.fk_B a
  </code></pre>