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Unformatted text preview: HW #5 Salim Sarımurat 29.12.2009 S. 1. a. 2 b. c. 3 d. e. 4 S. 2. It is not possible to express that the tests on a plane must be conducted by a technician who is an expert on that model because the constraint is on the Entities. We can do this by dividing different expertise of technicians and the models but this would limit adding new models and expertise types of the technicians. 5 Manager Employee S. 3. 1. Employee’s employee‐name attribute is assumed as primary key. 2. Company’s company‐name attribute is assumed as primary key. 3. Employees’ should work in at least one company. 4. Companys’ should have at least one Employee. 5. Employees’ can have at most one manager. 6 S. 4. a) πemployee‐name (σcompany‐name = “Microsoft” (Works)) b) πemployee‐name, city (Employee (σcompany‐name = “Microsoft” (Works))) c) πemployee‐name, street, city ( σ( company‐name = “Microsoft” d) πemployee‐name, employee‐name(σcompany‐name = company‐name (Works x Works)) e) πemployee‐name(Employee Works Company) f) πemployee‐name((Employee MANAGES) (manager‐name = employee2.employee‐name employee.city = employee2.city) (ρemployee2(Employee))) g) Based on the 3rd assumption that we have made in S.3. above; salary > “10000”) (Works Employee)) employee.street = employee2.street πemployee‐name(σcompany‐name ≠ “First Bank Corporation”(Works)) Otherwise, it would be; πemployee‐name(Employee) ‐ πemployee‐name(σcompany‐name = “First Bank Corporation”(Works)) h) πemployee‐name(Works) − (πWorks.employee‐name(Works (Works.salary ≤ Works2.salary Corporation”) ρWorks2 (Works))) i) πompany‐name(Company ÷ (πCity(σcompany‐name = “Small Bank Corporation”(Company)))) j) πemployee‐name((Manages) (Employee.employee‐name = Manages.manager‐name)(Employee) (company‐name = “Microsoft”)( Works)) works2.company‐name = “Small Bank ...
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This note was uploaded on 12/01/2011 for the course CS 351 taught by Professor Fazlıcan during the Spring '11 term at Bilkent University.
- Spring '11