# Exercise 1 Relational Algebra Database System-dww.

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Exercise 1 Relational Algebra Database System-dww

6 Relations of Company

Database System-dww Exercises (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.

Database System-dww Exercises (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. (i) Find the names and addresses of employees who work on at least one project located in Houston but whose department has no location in Houston. List the last names of department managers who have no dependents.

(a) Retrieve the names of employees in department 5 who work more than 10 hours per week on the 'ProductX' project Graphical approach can be used to help the logical and prosedural approach Example of above query, the graphical approach: clue from query the relations that (may) work on the query are in the red text Database System-dww P ProductX Pname=‘ProductX’ WE > 10 Hours > 10 Pnumber=Pno 5 Dno = 5 ESSN=SSN Fname, Lname (?) WORKS_ON_ProductX (Rel.A)  (PNAME=‘ProductX’(PROJECT) PNUMBER=PNO(WORKS_ON)) EMPLOYEE_DEPT5_WORKS_MORE_10_onProductX (Rel.B)  ((EMPLOYEE) SSN=ESSN(HOURS>10(Rel.A))) RESULT  FNAME,LNAME(DNO=‘5’ (Rel.B))

List the names of employees who have a dependent with the same first name as themselves. Graphical approach Database System-dww DpE Depend_name=Fname Fname, Lname (?) ESSN=SSN RESULT  FNAME,LNAME(DEPENDENT (ESSN,DEPEND_NAME)=(SSN,FNAME)(EMPLOYEE))

(c) Find the names of employees that are directly supervised by 'Franklin Wong'. Graphical for next questions (try by Urself) Database System-dww E_SSN_FRANKLIN_WONG(Rel.A)  (SSN(FNAME=‘FRANKLIN’ LNAME=‘WONG’(EMPLOYEE))) E_SUPERVISED_BY_FRANKLIN_WONG (Result)  (FNAME, LNAMES(EMPLOYEE) SUPERSSN=SSN(Rel.A))

(d) For each project, list the project name and the total hours per week (by all employees) spent on that project Using function Database System-dww TOTAL_HOURS_PROJECT (Rel.A)  (PNO ℱ SUM HOURS(WORKS_ON)) RESULT  (PNAME, TOT_HOURS(Rel.A) PNO=PNUMBER(PROJECT))

(e) Retrieve the names of employees who work on every project Database System-dww ALL_EMPLOYEE(SSN, PNO)(Rel.A)  (SSN, PNO(WORKS_ON)) ALL_PROJECT(PNO)(Rel.B)  (PNO(PROJECT)) E_ALL_PROJECT  (Rel.A÷Rel.B) RESULT  (FNAME, LNAME (E_ALL_PROJECT * EMPLOYEE))

(f) Retrieve the names of employees who do not work on any project Database System-dww ALL_EMPLOYEE(SSN)(Rel.A)  (SSN(EMPLOYEE)) ALL_EMPLOYEE_WORKING(SSN)(Rel.B)  (ESSN(WORKS_ON)) E_NOT_WORKING  (Rel.A - Rel.B) RESULT  (FNAME, LNAME ( (EMPLOYEE) SSN=ESSN(E_NOT_WORKING))

(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 Database System-dww AVERAGE_SALARY_DEPARTMENT(Rel.A)  (DNO ℱ AVG SALARY(EMPLOYEE)) RESULT  (DNO, AVG_SALARY(Rel.A * EMPLOYEE)) RESULT   ℱ AVG SALARY(SEX=‘F’(EMPLOYEE))

(i) Find the names and addresses of employees who work on at least one project located in Houston but whose department has no location in Houston Database System-dww E_WORK_PROJ_IN_HOUSTON(Rel.A)  (ESSN(WORKS_ON) PNO=PNUMBER (PLOCATION=‘HOUSTON’(PROJECT))) E_D_NOT_IN_HOUSTON(Rel.B)  (SSN(EMPLOYEE) DNO=DNUMBER (DLOCATION≠‘HOUSTON’(DEPARTMENT_LOCATIONS))) RESULT  (FNAME, LNAME, ADDRESS((EMPLOYEE) (Rel.A-Rel.B))

(j)List the last names of department managers who have no dependents Database System-dww D_MNG_SSN(Rel.A)  (SSN(DEPARTMENT) E_WITH_DEPENDENT(Rel.A)  (SSN(DPENDENT) MNGR_NO_DEPENDENT  (Rel.A – Rel.B) RESULT  (LNAME(EMPLOYEE * MNGR_NO_DEPENDENT))