MySQL Multiple-Table Query Question?

Question

I am supposed to list the book codes for each pair of books that have the same price. The first book_code listed should be the major sort key and the second book_code should be the minor sort key. They give an example of a pair being Book_Code 0200 and 7599 because both books are $8.00 for this problem. 

I am not even sure how to really start this because it sounds simple enough yet I am sure it is more complicated than I am thinking it is going to be. 

Here is an example of the coding I have for a different problem so that you guys can see what the tables and columns are called...

select Book_Code, Title, Price
from Book
join Publisher on Publisher.Publisher_Code = Book.Publisher_Code 
where Publisher.Publisher_Code = 'PL';

The Eskimo · Accepted Answer

select distinct Book_Code, Price

from Book b1, Book b2

where

b1.Publisher_Code <> b2.Publisher_Code and

b1.Price = b2.Price

This should work!

It lists all pairs (sets) of books that have the same price.

P.S. select price also from the table so that Book_Code will be from b1 and Price will be from b2 though b1.price will be same as b2.price. Think it will work now!