title: sql oracle Union with null values
body: <p>I have a query on 2 views which when it unions</p>
  
  <p>View X</p>
  
  <pre><code>A    B    C
  
  2    3
  </code></pre>
  
  <p>View Y</p>
  
  <pre><code>A    B    C
  
       3    4
  </code></pre>
  
  <p>this is my query from the 2 views</p>
  
  <pre><code>select * from view X
  UNION 
  select * from view Y;
  </code></pre>
  
  <p>the result I had: </p>
  
  <pre><code>A    B    C
  
  2    3   
  
       3    4
  </code></pre>
  
  <p>the result I wanted (the 2 overrides the null value in view Y @ attribute A): </p>
  
  <pre><code>A    B    C
  
  2    3   
  
  2    3    4
  </code></pre>
  
  <p>how can i obtained that ?</p>