C H A P T E R

3

SQL

Chapter 3 covers the relational language SQL. The discussion is based on SQL:1999. Integrity constraint and authorization features of SQL being a large language, many of its features are not covered here, and are not appropriate for an introductory course on databases. Standard books on SQL, such as Date and Darwen [1993] and Melton and Simon [1993], or the system manuals of the database system you use can be used as supplements for students who want to delve deeper into the intricacies of SQL. Although it is possible to cover this chapter using only handwritten exercises, we strongly recommend providing access to an actual database system that supports SQL. A style of exercise we have used is to create a moderately large database and give students a list of queries in English to write and run using SQL. We publish the actual answers (that is the result relations they should get, not the SQL they must enter). By using a moderately large database, the probability that a “wrong” SQL query will just happen to return the “right” result relation can be made very small. This approach allows students to check their own answers for correctness immediately rather than wait for grading and thereby it speeds up the learning process. A few such example databases are available on the Web home page of this book. Exercises that pertain to database design are best deferred until after Chapter 7.

Exercises
3.8 Consider the insurance database of Figure 3.11, where the primary keys are underlined. Construct the following SQL queries for this relational database. a. Find the number of accidents in which the cars belonging to “John Smith” were involved. b. Update the damage amount for the car with license number “AABB2000” in the accident with report number “AR2197” to $3000. Answer: Note: The participated relation relates drivers, cars, and accidents.