title: Combine multiple rows into 1 row
body: <p>Say for example I have a table that contains a description of a customer's activities while in a cafe. (Metaphor of the actual table I am working on)</p>
  
  <pre><code>Customer    Borrowed Book   Ordered Drink   Has Company
  1               1       
  1                                1  
  1                                               Yes
  2                                1  
  3                                1  
  3                                               Yes
  4               1                1  
  4                                1  
  </code></pre>
  
  <p>I wish to combine the rows in this way</p>
  
  <pre><code>Customer    Borrowed Book   Ordered Drink   Has Company
  1               1                 1            Yes
  2                                 1 
  3                                 1            Yes
  4               1                 2
  </code></pre>
  
  <p>I did self join with coalesce, but it did not give my desired results.</p>