Home > 2.6 Construct appropriate tables for each of the E-R diagrams in Exercises 2.2 to 2.4.

# 2.6 Construct appropriate tables for each of the E-R diagrams in Exercises 2.2 to 2.4.

2.6 Construct appropriate tables for each of the E-R diagrams in Exercises 2.2 to 2.4.

2.7 Design an E-R diagram for keeping track of the exploits of your favorite sports team. You should store the matches played, the scores in each match, the players in each match and individual player statistics for each match. Summary statistics should be modeled as derived attributes.

2.20 Design a generalization-specialization hierarchy for a motor-vehicle sales company. The company sells motorcycles, passenger cars, vans, and buses. Justify your placement of attributes at each level of hierarchy. Explain why they should not be placed at a higher or lower level.

3.3 Design a relational database corresponding to the E-R diagram of Figure 3.38.

3.10 Consider the relational database of Figure 3.39. Give a relational-algebra expression for each of the following queries:

a. Find the company with the most employees.

b. Find the company with the smallest payroll.

c. Find those companies whose employees earn a higher salary, on average, than the average salary at First Bank Corporation.

(Supplements - information needed for answering 2.6)

2.2 Construct an E-R diagram for a car-insurance company whose customers own one or more cars each. Each car has associated with it zero to any number of recorded accidents.

2.3 Construct an E-R diagram for a hospital with a set of patients and a set of medical doctors. Associate with each patient a log of the various tests and examinations conducted.

2.4 A university registrar's office maintains data about the following entitites: (a) courses, including number, title, credits, syllabus, and prerequisites; (b) course offerings, including course number, year, semester, section number, instructor(s), timings, and classroom; (c) students, including student-id, name, and program; and (d) instructors, including identification number, name, department, and title. Further, the enrollment of students in courses and grades awarded to students in each course they are enrolled for must be appropriately modeled. Construct an E-R diagram for the registrar's office. Document all aassumptions that you make about the mapping constraints.

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