title: Postgresql, select empty fields
body: <p>I'm trying to get empty "text" fields from my table which I cleared manually with pgadmin.
  Initially in those fields was '' and I can query them like this:</p>
  
  <pre><code>SELECT mystr, mystr1 FROM mytable WHERE mystr='' or mystr1=''
  </code></pre>
  
  <p>But that not work if I delete text from them and leave cells blank.</p>
  
  <p>How to write query to get those '' and clear cells together in result?
  Or clear cells alone?</p>