title: Oracle can I use parallel hint in subquery?
body: <p>I have many complex select statements to run, which will take at least 2 hours, and I want to speed up the query.
  Can I use parallel hint both in subquery and mainquery to improve performance?
  For example, is the following valid?</p>
  
  <pre><code>select /*+ parallel(32) */
      a.id,
      (select /*+ parallel(32) */ b.col1 from table b where b.id = a.id)
  from 
  (select /*+ parallel(32) */ c.id, c.col2 
   from table c) a
  </code></pre>
  
  <p>I am new to parallel hints. Thank you in advance for your advice.</p>