title: DB2: How to concatenate null strings in DB2?
body: <p>I have to concatenate 2 columns (ex. FIRSTANME and LASTNAME).<br>
  I do it this way: </p>
  
  <pre><code>FIRSTNAME || ' ' || LASTNAME`.   
  </code></pre>
  
  <p>If one of them is null, but the other one is not null, I get null as concatenation result.<br>
  And I want following behavior </p>
  
  <pre><code>FIRSTNAME = null and LASTNAME = "Smith" ==&gt; 
    FIRSTANME || ' ' || LASTNAME == ' Smith'. 
  </code></pre>
  
  <p>How to solve this in DB2?</p>