title: adding a column with sequence data to table based on repeating events
body: <p>I'm learning MySQL (via mode) and am approaching the Advanced section. I have a dataset that contains events that recur and I want to add a column that identifies the first, second, third, fourth, etc (no limit) occurrence of the events for that day.</p>
  
  <pre><code>CustomerID     ActivityType     Day     Sequence
  Adam           Inquiry          1       1
  Barb           Inquiry          1       2
  Adam           Inquiry          1       3
  Charlie        Inquiry          1       4
  Barb           Order            1       5
  Charlie        Inquiry          1       6
  Adam           Inquiry          1       7
  Barb           Order            1       8
  </code></pre>
  
  <p>I've searched here for problems that seem similar, to help focus my learning but I don't see anything quite the same.</p>
  
  <p>My desired output would be the same as above but with an added column that shows the sequence of recurring combinations of customer and activity, like this:</p>
  
  <pre><code>CustomerID     ActivityType     Day     Sequence  Recur
  Adam           Inquiry          1       1         1
  Barb           Inquiry          1       2         1
  Adam           Inquiry          1       3         2
  Charlie        Inquiry          1       4         1
  Barb           Order            1       5         1
  Charlie        Inquiry          1       6         2
  Adam           Inquiry          1       7         3
  Barb           Order            1       8         2
  </code></pre>