title: How many trucks came empty but bought something
body: <p>I think this is the hardest to date I have had to crack - so hard I had a hard time finding a good headline.</p>
  
  <p>So we have a site where trucks come and buy say Gravel, or sand or other building materials.</p>
  
  <p>Sometimes they also unload demolition waste first.</p>
  
  <p>I need to find out a couple of things</p>
  
  <ol>
  <li>how many trucks (and from what companys) came empty </li>
  <li>if they came empty what did they buy from us.</li>
  <li>what companys are sending full trucks and what are sending empty trucks.</li>
  <li>a tope 10 of materials they will drive to us from to buy even when coming empty to our facility.</li>
  <li>a list of all the order numbers that they drove to us til fill and came with empty trucks. ( I have distances linked to order numbers, so now I can estimate the value of our products)</li>
  </ol>
  
  <p>The data I have available:
  I have a full data set of when what customer buys what and / or pay to deliver.
  E.G.:</p>
  
  <p><a href="https://i.stack.imgur.com/MFWMn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MFWMn.png" alt="Example of how data looks"></a></p>
  
  <p>I can see the parts I need to split the data into I think it should be something like this</p>
  
  <ol>
  <li>find all unique licence plates</li>
  <li>somehow map if they bought materials within 30 minutes of
  offloading demolition waste (most trucks will come between 2 and 10
  times per day)</li>
  <li>Present all this data (on a normal day we have about 800 trucks = 2000 lines since they weigh in, weigh out, and then some buy something = 2 more weigh lines)</li>
  </ol>
  
  <p>I can easily find unique licence plates per day (either by formula or by Excel function Data/delete doublets, 
  but after that I have no clue where to start.</p>
  
  <p>I think I need some sheets in between, where I somehow mark if a material was bought from an "empty truck" and I need a counter for that .. somehow...</p>
  
  <p>Any help on how to get started is appreciated.</p>