title: SQL query query
body: <p>SQL query to get list of Authors who have written at least a book on all Genres</p>
  
  <p>Tables are     </p>
  
  <pre><code>      Author_id  |  Author_info  =&gt; authors
        Genre_id   |  Genre_info   =&gt; genres
        Author_id  |  Genre_id  |  Book_id  =&gt; books
  </code></pre>
  
  <p>I'm using Mysql, what would be the best way to do this?</p>