[Normalization: join dependency] Consider a table Sales of three columns shown below.

The intent of this table design is to keep the following three kinds of information in one table: (a) an agent represents a company, (b) an agent sells a product, and (c) a company makes a product. Suppose there is a rule that an agent sells a product made by the company the agent represents.

a) Express the rule in terms of join dependency. Specify the relations involved in the join dependency constraint.

b) Given the join dependency, if we insert another row, to the tables Sales, we are not done. State what more should be done and why.

c) State how we can eliminate the update anomaly as observed in the exercise b.

AgentCompany Product Smith Ford Smith GM Jones Car Car Truck GM AgentCompany Product Smith Ford Smith GM Jones Car Car Truck GM