title: Fluent Nhibernate - selecting specific column and count query with group by
body: <p>I'm having some trouble excuting a query in fluent nhibernate.
  I have a table : Books with the following columns:</p>
  
  <pre><code>ID, NAME, YEAR, BOOK_TYPE, AUTHOR_ID
  </code></pre>
  
  <p>I want to excute the following sql query in Fluent NHibernate:</p>
  
  <pre><code>SELECT BOOK_TYPE, COUNT(*)
  FROM BOOKS
  GROUP BY BOOK_TYPE
  </code></pre>