title: Postgresql 9.6. Check if a field is empty
body: <p>In Postgresql 9.6, I have a table like this:</p>
  
  <pre><code>ID  ADDRESS_1  ADDRESS_2
   1    bac1       def2
   2    bac2  
  </code></pre>
  
  <p>If I execute this</p>
  
  <pre><code>SELECT exists (SELECT ADDRESS_2 FROM my_table WHERE ADDRESS_1='bac3');
  </code></pre>
  
  <p>I get False answer (expected)</p>
  
  <p>However, if I execute this</p>
  
  <pre><code>SELECT exists (SELECT ADDRESS_2 FROM my_table WHERE ADDRESS_1='bac2');
  </code></pre>
  
  <p>I get True answer (Not expected)</p>
  
  <p>I reckon it is because there is a Null value.</p>
  
  <p>So my objective is to obtain False value for the last one.</p>
  
  <p>Any ideas or thoughts?</p>
  
  <p>Thank you in advance</p>