title: translation from Datalog to SQL
body: <p>I am still thinking on how to translate the recursivity of a Datalog program into SQL, such as</p>
  
  <pre><code>P(x,y) &lt;- Q(x,y).
  Q(x,y) &lt;- P(x,z), A(y).
  </code></pre>
  
  <p>where <code>A/1</code> is an EDB predicate. This, there is a co-dependency between <code>P</code> and <code>Q</code>. For longer queries, how to solve this problem?</p>
  
  <p>Moreover, is there any system completely implement the translation? If there is, may I know what system or which paper may I refer?</p>