9.1 (Repeated from the body of the chapter.) Check that joining any pair of the binary relations shown in Figure 9-2 yields a result containing a “spurious” tuple (i.e., a tuple not appearing in Figure 9-1) and that joining the third binary relation to that intermediate result then eliminates that spurious tuple.

9.2 Write a Tutorial D CONSTRAINT statement to express the JD that holds in relvar SPJ as discussed in the body of the chapter.

9.3 Design a database for the following. The entities to be represented are sales representatives, sales areas, and products. Each representative is responsible for sales in one or more areas; each area has one or more responsible representatives. Each representative is responsible for sales of one or more products, and each product has one or more responsible representatives. Each product is sold in one or more areas, and each area has one or more products sold in it. Finally, if representative r is responsible for area a, and product p is sold in area a, and representative r sells product p, then r sells p in a.

9.4 Give an example from your own work environment, if possible, of a relvar in BCNF but not 5NF.