title: Use of primary key in the DWH / Dimensional Model beyond to search functionality
body: <p>I work currently in a DWH where the OLTP Database deliver the Data, and I ve noticed that from the input layer to the core of the DWH.</p>
  
  <p>we make the following transformation </p>
  
  <ul>
  <li>we add a Pk and we normalize the Data in 1NF </li>
  <li>We add a historic Column.</li>
  </ul>
  
  <p>For example</p>
  
  <pre><code>Table client:
  
      id_client is the primary key
  
      id_client |client | Date     |Subsidary ..
    -------------------------------------------------
       000001   |vha57  | 19-08-18 | Detutsche Bank
  </code></pre>
  
  <p>The interesting thing is that we dont use the primary key(Client ID) to retrun a value, in fact i never see it used.</p>
  
  <p>If you want to search a row you use the client and Date</p>
  
  <pre><code>     select  colum1,column2 from client where client = 'vha57' and Date = '19-08-18'
  </code></pre>
  
  <p>I wonder why we have to add a primary key if they dont have a search use.
  Does PK have another use apart from to localizated a specific row? </p>