title: Accept only restricted characters using accept in oracle
body: <p>i need to accept only Y/N for is_master variable declare below.</p>
  
  <p>For example if i use the below statement in SQL script the user can enter any character.</p>
  
  <p>I want to restrict user to enter only y Y n or N</p>
  
  <pre><code>Accept is_master prompt ' Is the user a Master user (Y/N)  : '
  </code></pre>