Hi,
I have 4 columns, as you can see below (Excel)
<colgroup><col><col><col><col></colgroup><tbody>
CustomerID
TransactionDate
Amount
Date of 1st purchase
19
19/12/2016
131.5
19/12/2016
1465
24/12/2016
73.44
24/12/2016
2389
25/12/2016
49
25/12/2016
367
26/12/2016
25.9
26/12/2016...