17.8. Dr. Codd’s T-Join
Dr. E. F. Codd introduced a set of new theta operators, called Toperators, which were based on the idea of a best-fit or approximate equality (Codd 1990). The algorithm for the operators is easier to understand with an example modified from Dr. Codd (Codd 1990).
The problem is to assign the classes to the available classrooms. We want (class_size < room_size) to be true after the assignments are made. This will allow us a few empty seats in each room for late students. We can do this in one of two ways. The first way is to sort the tables in ascending order by classroom size and the number of students in a class. We start with the following tables:
CREATE TABLE Rooms (room_nbr CHAR(2) PRIMARY KEY, room_size INTEGER NOT ...