Getting the total quantity of each item in a table

Databases
1

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

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!!!

2 
SELECT
    BookID
  , COUNT(*) AS Total
FROM Purchases
GROUP BY BookID
3

Hi guido2004,

One last question please. Where are the result stored and how can I read them?
I understand I have to run this query and assign a variable to the result.
Is this result an array, having the totals of each BookID per rows?

Thanks a lot for your answer!!

4

What language are you using? As that question may be better suited in the appropriate forum. If you are using PHP, are you utilizing PDO, MySQLi, MySQL?

5

Sorry, I am using PHP and MySQL.

Thanks a lot!

6

Okay, well then you can utilize several different options.
[fphp]mysql_ fetch_ array[/fphp], [fphp]mysql_ fetch_ assoc[/fphp], and [fphp]mysql_fetch_row[/fphp]

All of the above options have examples of how to use them.