title: Select rows with same id but different value in another column
body: <p>I tried for hours and read many posts but I still can't figure out how to handle this request:</p>
  
  <p>I have a table like this:</p>
  
  <pre><code>+------+------+
  |ARIDNR|LIEFNR|
  +------+------+
  |1     |A     |
  +------+------+
  |2     |A     |
  +------+------+
  |3     |A     |
  +------+------+
  |1     |B     |
  +------+------+
  |2     |B     |
  +------+------+
  </code></pre>
  
  <p>I would like to select the ARIDNR that occurs more than once with the different LIEFNR.</p>
  
  <p>The output should be something like:</p>
  
  <pre><code>+------+------+
  |ARIDNR|LIEFNR|
  +------+------+
  |1     |A     |
  +------+------+
  |1     |B     |
  +------+------+
  |2     |A     |
  +------+------+
  |2     |B     |
  +------+------+
  </code></pre>