title: Concatenate data from two fields ignoring NULL values in one of them?
body: <p>Dataset is following:</p>
  
  <pre><code>FirstName          LastName       city      street        housenum
  john            silver            london   ukitgam         780/19
  gret            garbo             berlin   akstrass         102
  le              chen             berlin    oppenhaim        NULL
  daniel          defo             rome      corso vinchi     25
  maggi           forth           london     bolken str      NULL
  voich           lutz            paris      pinchi platz     NULL
  anna           poperplatz        milan     via domani       15/4
  </code></pre>
  
  <p>write following query: </p>
  
  <pre><code>SELECT Trim(a.FirstName) &amp; ' ' &amp; Trim(a.LastName) AS employee_name,
  a.city, a.street + ' ' + a.housenum AS address
  FROM Employees AS a 
  </code></pre>
  
  <p>The result will be as this:</p>
  
  <pre><code>employee_name        city          address
  john silver         london       ukitgam 780/19
  gret garbo          berlin       akstrass 102
  le chen             berlin       NULL
  daniel defo         rome        corso vinchi 25
  maggi forth         london       NULL
  voich lutz          paris        NULL
  anna poperplatz     milan      via domani 15/4
  </code></pre>
  
  <p>but I want this:</p>
  
  <pre><code>employee_name           city                  address
  john silver            london               ukitgam 780/19
  gret garbo             berlin               akstrass 102
  le chen                berlin               oppenhaim
  daniel defo            rome                corso vinchi 25
  maggi forth            london              bolken str
  voich lutz             paris               pinchi platz
  anna poperplatz        milan             via domani 15/4
  </code></pre>
  
  <p>please help me.</p>