title: How to check compatible and optimizer version for a Oracle database
body: <p>How to check compatible and optimizer version for a Oracle database instance. I want to know if there is any specific command to check the above two versions from SqlPlus. For compatible version, I know following command might do the job:</p>
  
  <pre><code>select * from database_compatible_level;
  </code></pre>
  
  <p>I want similar command which will tell me optimizer version. Please help.</p>