title: Concatenate columns together, columns can be null
body: <p>I need to bring values together and copy it to a diffrent column.</p>
  
  <pre><code>COLUMN 1 | COLUMN 2 |  COLUMN 3 | COLUMN 4 
  Hallo      out         there      Hallo out there
  My         NULL        name is    My name is
  I'm        a           rabbit     I'm a rabbit
  </code></pre>
  
  <p>How to merge column 1, 2, 3 and copy it to column4 separated with space.</p>
  
  <p>Columns can be null.</p>