I am downloading a spreadsheet file from a website database. Each row is a customer/transaction record: the customer's contact info, payment amount and method, and in a series of fields (columns) what the customer purchased -- say, a book, a knife, a ticket to Paris, most represented by two fields (item and quantity).
What I am aiming at is to transform each such customer/transaction row into a list of purchases, that is, several rows for each customer: customer/transaction id, item purchased. All in a long table of purchases for all customers/transactions.
For some reason, my mind is really struggling with how to get from where I am (a list of customer transactions) to a list of items purchased tagged with a customer/transaction id. I am drawing a blank on a strategy and am hoping that someone can point me in the right direction.