Good day,

I am working in an online website for selling books.

There is a table where the sold books are stored, like this:

Purchases

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id | int - autoincrement

Date

CustomerID (foreing key to table Customers)

BookID (foreign key to table Books)

How can I calculate the total quantity of sold books of each one?

For instance, having 'n' books, how many BookID = 1 to n have been sold (how many of each one)?

Thanks a lot!!!