title: SQL String contains ONLY
body: <p>I have a table with a field that denotes whether the data in that row is valid or not. This field contains a string of undetermined length. I need a query that will only pull out rows where all the characters in this field are N. Some possible examples of this field.</p>
  
  <pre><code>NNNNNNNNNNNNNNNNNNN
  NNNNNNNNNNNNNNNNNNNNNNN
  NNNNNEEEENNNNNNNNNNNN
  NNNNNOOOOOEEEENNNNNNNNNNNN
  </code></pre>
  
  <p>Any suggestions on a postcard please.</p>
  
  <p>Many thanks</p>