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COMP3030 Database Management System Final Review

COMP3030 Database Management System Final Review. AGENDA. Ch1. Introduction Ch2. Relational Model Ch3. SQL Ch4. Advanced SQL Ch6. Database Design and the ER model Ch7. Relational Database Design Ch10. XML. CH2 EXERCISES.

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COMP3030 Database Management System Final Review

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  1. COMP3030 Database Management SystemFinal Review

  2. AGENDA • Ch1. Introduction • Ch2. Relational Model • Ch3. SQL • Ch4. Advanced SQL • Ch6. Database Design and the ER model • Ch7. Relational Database Design • Ch10. XML

  3. CH2 EXERCISES • Given two relations R1 and R2, where R1 contains N1 tuples, R2 contains N2 tuples, and N2 > N1 > 0, give the min and max possible sizes for the resulting relational algebra expressions:(1) R1UR2, (2) R1∩R2, (3) R1−R2, (4) R1×R2, (5) σa=5(R1), and (6) πa(R1)

  4. CH2 EXERCISES • Consider the Supplier-Parts-Catalog schema from the previous question. State what the following queries compute: • Find the Supplier names of the suppliers who supply a red part that costs less than 100 dollars. • This Relational Algebra statement does not return anything • Find the Supplier names of the suppliers who supply a red part that costs less than 100 dollars and a green part that costs less than 100 dollars.

  5. Ch6 EXERCISES • Consider the Supplier-Parts-Catalog schema from the previous question. State what the following queries compute: • Find the Supplier ids of the suppliers who supply a red part that costs less than 100 dollars and a green part that costs less than 100 dollars.

  6. AGENDA • Ch1. Introduction • Ch2. Relational Model • Ch3. SQL • Ch4. Advanced SQL • Ch6. Database Design and the ER model • Ch7. Relational Database Design • Ch10. XML

  7. CH3 EXERCISES • What is the difference between a candidate key and the primary key for a given relation? What is a superkey? • The primary key is the key selected by the DBA from among the group of candidate keys, all of which uniquely identify a tuple. A superkey is a set of attributes that contains a key.

  8. CH3 EXERCISES • Answer each of the following questions briefly. The questions are based on the following relational schema: Emp(eid: integer, ename: string, age: integer, salary: real) Works(eid: integer, did: integer, pcttime: integer) Dept(did: integer, dname: string, budget: real, managerid: integer) 1. Give an example of a foreign key constraint that involves the Dept relation. What are the options for enforcing this constraint when a user attempts to delete a Dept tuple? • Consider the following example. It is natural to require that the did field of Works should be a foreign key, and refer to Dept. CREATE TABLE Works ( eid INTEGER NOT NULL , did INTEGER NOT NULL , pcttime INTEGER, PRIMARY KEY (eid, did), FOREIGN KEY (did) REFERENCES Dept )

  9. CH3 EXERCISES • 2. Write the SQL statements required to create the preceding relations, including appropriate versions of all primary and foreign key integrity constraints.

  10. CH3 EXERCISES • 3. Define the Dept relation in SQL so that every department is guaranteed to have a manager. • CREATE TABLE Dept ( did INTEGER, budget REAL, managerid INTEGER NOT NULL , PRIMARY KEY (did), FOREIGN KEY (managerid) REFERENCES Emp)

  11. CH3 EXERCISES • 4. Write an SQL statement to add John Doe as an employee with eid = 101, age = 32 and salary = 15, 000. • INSERT INTO Emp (eid, ename, age, salary)VALUES (101, ’John Doe’, 32, 15000)

  12. CH3 EXERCISES • 5. Write an SQL statement to give every employee a 10 percent raise. • UPDATE Emp ESET E.salary = E.salary * 1.10

  13. CH3 EXERCISES • 6. Write an SQL statement to delete the Toy department. Given the referential integrity constraints you chose for this schema, explain what happens when this statement is executed. • DELETEFROM Dept DWHERE D.dname = ’Toy’

  14. CH3 EXERCISES • Consider the following schema: Suppliers(sid: integer, sname: string, address: string) Parts(pid: integer, pname: string, color: string) Catalog(sid: integer, pid: integer, cost: real)The Catalog relation lists the prices charged for parts by Suppliers. Write the following queries in SQL: 1. Find the pnames of parts for which there is some supplier. • SELECT DISTINCT P.pnameFROM Parts P, Catalog CWHERE P.pid = C.pid 5. Find the sids of suppliers who charge more for some part than the average cost of that part (averaged over all the suppliers who supply that part). • SELECT DISTINCT C.sidFROM Catalog CWHERE C.cost > ( SELECT AVG (C1.cost) FROM Catalog C1 WHERE C1.pid = C.pid )

  15. Ch3 EXERCISES 8. Find the sids of Suppliers who supply a red parts and a green part SELECT DISTINCT C.sid FROM Catalog C, Parts P WHERE C.pid = P.pid AND P.color = ‘Red’ INTERSECT SELECT DISTINCT C1.sid FROM Catalog C1, Parts P1 WHERE C1.pid = P1.pid AND P1.color = ‘Green’ 9. Find the sids of Suppliers who supply a red parts or a green part SELECT DISTINCT C.sid FROM Catalog C, Parts P WHERE C.pid = P.pid AND P.color = ‘Red’ UNION SELECT DISTINCT C1.sid FROM Catalog C1, Parts P1 WHERE C1.pid = P1.pid AND P1.color = ‘Green’

  16. AGENDA • Ch1. Introduction • Ch2. Relational Model • Ch3. SQL • Ch4. Advanced SQL • Ch6. Database Design and the ER model • Ch7. Relational Database Design • Ch10. XML

  17. CH6 EXERCISES • A university database contains information about professors (id. by SSN) and courses (id. by courseid). Professors teach courses; each of the following situations concerns the Teaches relationship set. For each situation, draw an ER diagram that describes it (assuming no further constraints hold). • Professors can teach the same course in several semesters, and each offering must be recorded.

  18. Professors can teach the same course in several semesters, and only the most recent such offering needs to be recorded. (Assume this condition applies in all subsequent questions.)

  19. Every professor must teach some course.

  20. Every professor teaches exactly one course (no more, no less).

  21. Every professor teaches exactly one course (no more, no less), and every course must be taught by some professor.

  22. Certain courses can be taught by a team of professors jointly, but it is possible that no one professor in a team can teach the course. Model this situation, introducing additional entity sets and relationship sets if necessary.

  23. 2.4 A company database needs to store information about employees (identified by ssn, with salary and phone as attributes), departments (identified by dno, with dname and budget as attributes), and children of employees (with name and age as attributes). Employees work in departments; each department is managed by an employee; a child must be identified uniquely by name when the parent (who is an employee; assume that only one parent works for the company) is known. We are not interested in information about a child once the parent leaves the company.

  24. Convert ER diagram to relational schema • Employee (ssn, salary, phone, mangerid) • Departments (dno, dname, budget) • Child (name, age, ssn) • Works_in (ssn, dno)

  25. AGENDA • Ch1. Introduction • Ch2. Relational Model • Ch3. SQL • Ch6. Database Design and the ER model • Ch7. Relational Database Design • Ch10. XML

  26. CH7 EXERCISES A relation R is in third normal form if for every functional dependency of the form X  A one of the following statements is true: • A Є X that is, A is a trivial functional dependency , or (1) • X is a superkey, or (2) • A is part of some key for R (3) A relation R is in BCNF if (1) or (2)

  27. CH7 EXERCISES • 7.2. Consider a relation R with five attributes ABCDE. You are given the following dependencies: • A → B, BC → E, ED → A • List all candidate keys for R. • CDE, ACD, BCD • Is R in 3NF? • R is in 3NF because B, E and A are all parts of candidate keys. • Is R in BCNF? • R is not in BCNF because none of A, BC and ED contain a key.

  28. BCNF, 3NF decomposition • Canonical cover • Closure • 4NF

  29. AGENDA • Ch1. Introduction • Ch2. Relational Model • Ch3. SQL • Ch6. Database Design and the ER model • Ch7. Relational Database Design • Ch10. XML

  30. Give the DTD for an XML representation of the following nested-relational schema • Emp = (ename, ChildrenSet setof(Children), SkillsSet setof(Skills)) • Children = (name, Birthday) • Birthday = (day, month, year) • Skills = (type, ExamsSet setof(Exams)) • Exams = (year, city)

  31. <!DOCTYPE db [ • <!ELEMENT emp (ename, children*, skills*)> • <!ELEMENT children (name, birthday)> • <!ELEMENT birthday (day, month, year)> • <!ELEMENT skills (type, exams+)> • <!ELEMENT exams (year, city)> • <!ELEMENT ename( #PCDATA )> • <!ELEMENT name( #PCDATA )> • <!ELEMENT day( #PCDATA )> • <!ELEMENT month( #PCDATA )> • <!ELEMENT year( #PCDATA )> • <!ELEMENT type( #PCDATA )> • <!ELEMENT city( #PCDATA )> • ] >

  32. a. Find the names of all employees who have a child who has a birthday in March. for $e in /db/emp, $m in distinct($e/children/birthday/month) where $m = ’March’ return $e/ename

  33. b. Find those employees who took an examination for the skill type “typing” in the city “Dayton”. for $e in /db/emp $s in $e/skills[type=’typing’] $exam in $s/exams where $exam/city= ’Dayton’ return $e/ename

  34. c. List all skill types in Emp. for $t in /db/emp/skills/type return $t

  35. Final Exam Information • Ch1. Introduction • Ch2. Relational Model 17 • Ch3. SQL 41 • Ch4. Advanced SQL • Ch6. Database Design and the ER model 10 • Ch7. Relational Database Design 22 • Ch10. XML 10

  36. GOOD LUCK!!

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