Question

I’m working on developing a web portal for a bookstore, and I want to have the ability to suggest books to a user.

I want something similar to amazon.com, when a user orders book A, the system should provide a list of other suggested books. Book B is suggested if there exists a user Bob that bought both A and B. Additionally, I want my system to return the suggested books sorted on decreasing sales count, and only count sales to users that have bought both books (like Bob).

Here are the important tables:

Book(ISBN, title, publicationYear, etc..)

Orders(orderID, loginName, date)

BooksOrdered(orderID, ISBN, count)

This query is more complex than anything I’ve previously tried.

Current thoughts:

First find all the users that have ordered the same book (ISBN)

1. Join all three tables on Book.ISBN = BooksOrdered.ISBN AND Orders.orderID = BooksOrdered.ISBN
2. WHERE Book.ISBN = bookInQuestionISBN
3. GROUP BY Orders.loginName
4. Project out loginName

So something like:

SELECT Orders.loginName as otherBuyerLoginName
FROM Book, Orders, BooksOrdered,
WHERE Book.ISBN = bookInQuestionISBN AND Orders.orderID = BooksOrdered.ISBN
GROUP BY Orders.loginName

Then I could grab all the books these loginNames have ordered, group them by loginName, sum count and ORDER BY DESC SUM(BooksOrdered.count).

However, I’m thinking that the first result will most likely be the book in question. I don’t want to suggest the same book the user has just bought.

What do you suggest? Maybe I should start over from scratch?

EDIT:

Here is some data:

BooksOrdered contains:

orderID ISBN        count
    3   FakeISBN    3
    7   FakeISBN    3
    8   FakeISBN    100
    11  FakeISBN2   40
    7   FakeISBN2   4
    10  FakeISBN2   20
    10  FakeISBN3   34
    11  TesterISBN  3
    9   TesterISBN  1

Orders contains:

orderID loginName  date
2       Tester     2012-03-15 19:43:27
3       Tester     2012-03-16 15:56:55
6       Tester2    2012-03-16 17:28:02
7       Tester     2012-03-16 17:31:21
8       ni3hao3    2012-03-16 23:18:15
9       ni3hao3    2012-03-17 13:12:38
10      ni3hao3    2012-03-17 13:13:55
11      Bobby      2012-03-17 13:28:14

Alright, now I want to know the top suggestions for the book with ISBN = “TesterISBN”

Two people have ordered “TesterISBN”: ni3hao3 and Bobby

ni3hao3’s total sales history:

1 copy of "TesterISBN"
100 copies of "FakeISBN"
20 copies of "FakeISBN2"
34 copies of "FakeISBN3"

Bobby’s total sales history:

3 copies of "TesterISBN"
40 copies of "FakeISBN2"

So the totals of sales for purchasers of “TesterISBN” are as follows:

4 copies of "TesterISBN"
100 copies of "FakeISBN"
60 copies of "FakeISBN2"
34 copies of "FakeISBN3"

So I’d like the results to return:

FakeISBN
FakeISBN2
FakeISBN3

In that order.

EDIT:

I believe I’ve figured it out:

SELECT Bo.ISBN, B.title, SUM(Bo.count) 
FROM BooksOrdered Bo, Orders O, Book B
WHERE Bo.orderID = O.orderID AND Bo.ISBN = B.ISBN
                            AND Bo.ISBN != 'TesterISBN'
                            AND O.loginName IN ( SELECT DISTINCT(Orders.loginName) as otherBuyerLoginName
                            FROM Orders, BooksOrdered
                            WHERE BooksOrdered.ISBN = 'TesterISBN' 
                                AND Orders.orderID = BooksOrdered.orderID)
GROUP BY Bo.ISBN
ORDER BY SUM(Bo.count) DESC

Answer 1

SELECT Bo.ISBN, B.title, SUM(Bo.count) 
FROM BooksOrdered Bo, Orders O, Book B
WHERE Bo.orderID = O.orderID AND Bo.ISBN = B.ISBN
                            AND Bo.ISBN != 'TesterISBN'
                            AND O.loginName IN ( SELECT DISTINCT(Orders.loginName) as otherBuyerLoginName
                            FROM Orders, BooksOrdered
                            WHERE BooksOrdered.ISBN = 'TesterISBN' 
                                AND Orders.orderID = BooksOrdered.orderID)
GROUP BY Bo.ISBN
ORDER BY SUM(Bo.count) DESC

This seems to do the trick