CHAPTER 6: THE RELATIONAL ALGEBRA AND RELATIONAL CALCULUS Answers to Selected Exercises 6.15 Show the result of each of the example queries in Section 6.5 if they are applied to the database of Figure 5.6. Answer: (QUERY 1) Find the name and address of all employees who work for the 'Research' department. Result: FNAME LNAME ADDRESS John Smith 731 Fondren, Houston, TX Franklin Wong 638 Voss, Houston, TX Ramesh Narayan 975 Fire Oak, Humble, TX Joyce English 5631 Rice, Houston, TX (QUERY 2) For every project located in 'Stafford', list the project number, the controlling department number, and the department manager's last name, address, and birth date. Result: PNUMBER DNUM LNAME ADDRESS BDATE 10 4 Wallace 291 Berry, Bellaire, TX 20-JUN-31 30 4 Wallace 291 Berry, Bellaire, TX 20-JUN-31 (QUERY 3) Find the names of all employees who work on all the projects controlled by department number 5. Result: (empty because no tuples satisfy the result). LNAME FNAME (QUERY 4) Make a list of project numbers for projects that involve an employee whose last name is 'Smith' as a worker or as a manager of the department that controls the project. Result: PNO 1 2 (QUERY 5) List the names of all employees with two or more dependents. Result: LNAME FNAME Smith John Wong Franklin (QUERY 6) List the names of employees who have no dependents. Result: LNAME FNAME Zelaya Alicia Narayan Ramesh English Joyce Jabbar Ahmad Borg James (QUERY 7) List the names of managers who have at least one dependent. Result: LNAME FNAME Wallace Jennifer Wong Franklin
6.16 Specify the following queries on the database schema shown in Figure 5.5 using the relational operators discussed in this chapter. Also show the result of each query if applied to the database of Figure 5.6. (a) Retrieve the names of employees in department 5 who work more than 10 hours per week on the 'ProductX' project. (b) List the names of employees who have a dependent with the same first name as themselves. (c) Find the names of employees that are directly supervised by 'Franklin Wong'. (d) For each project, list the project name and the total hours per week (by all employees) spent on that project. (e) Retrieve the names of employees who work on every project. (f) Retrieve the names of employees who do not work on any project. (g) For each department, retrieve the department name, and the average salary of employees working in that department. (h) Retrieve the average salary of all female employees.
- Fall '08
- It, Relational model, Domain relational calculus, Relational calculus, Tuple relational calculus