title: Surrogate Keys in a Data Warehouse
body: <p>I understand the general concept of a surrogate key in a DWH environment.
  But there are two aspects I don't understand and couldn't find information about:</p>
  
  <ol>
  <li>Is it common practice that a surrogate key is unique in the <em>whole DWH</em> or unique <em>in one Dimension</em>?</li>
  <li>If I have a Dimension with a hierarchy, does that hierarchy influence the generation of the surrogate key?</li>
  </ol>