McMillan’s Quizzes Multiple choice, open book, open notes Not open computers, not open classmates Partial credit: if less than half the class gets a question right, he’ll give half-credit for the next best answer Not easy!

Of the following, which is an advantage of using a relational database? A.Attributes are inherited B.Relations are related to others hierarchically C.It is the only database approach that provides data independence D.It permits queries that are at least as powerful as relational algebra E.All of the above

Which of the following is uncharacteristic of a database schema? A. Attributes are not strongly typed B. Entities without a primary key C. A relation with a variable number of attributes D. It is unique to a database instance. E. All of the above

Professor Department WorksIn DeptHead since id dno since Of the following, what is implied by the heavy arrow from “Professor” to “WorksIn” A.Each department must have at least one professor B.All professors work in exactly one department C.Professors may be members of one or more departments D.All professors either work in, or head some department E.None of the above

Why is the ‘join’ operator not one of the five primitive (basic) operators of relational algebra? A.It was not included in Codd’s seminal papers B.Joins can be accomplished by composing primitive operations. C.It is equivalent to the Carteasian product D.It has too many variants to be considered a primitive operator. E.None of the Above

Which of the following best describes the result of this relational algebra statement? A. IDs of students who have taken at least two different courses B. IDs of students who have taken the same course twice C. IDs of students who have taken exactly one course D. IDs of students who have taken exactly two courses E. None of the above  StudID1 (  Course1  Course2 (  (T1(1  StudID1, 2  Course1, 3  Semester1, 4  Grade1), Transcript) ⋈ StudID1=StudID2  (T2(1  StudID2, 2  Course2, 3  Semester2, 4  Grade2), Transcript)))

Problem Points ER: binary, ternary, aggregate relationships. Problem: Represent supplier inventory, and who sells what to whom. Suppliers Orders Products

SQL: Aggregate Operators Example: sqlite> SELECT * FROM Sample; a|b 1|1 2|4 3|9 4|8 5|5 sqlite> SELECT a, MAX(b) FROM Sample; What does this return? Does it even run?

Relational Calculus – Some points TRC != DRC TRC Projection

4C: Find all classes in which no student failed (TRC) –Do with and without the universal quantifier CREATE TABLE Courses ( number TEXT, semester TEXT, seats INTEGER, PRIMARY KEY(number, semester) ); CREATE TABLE Enrollment ( student_name TEXT, course_number TEXT, course_semester TEXT, grade INTEGER, PRIMARY KEY(student_name, course_number, course_semester), FOREIGN KEY student_name REFERENCES Students(name), FOREIGN KEY (course_number, course_semester) REFERENCES Courses(number, semester) );

Questions? Database Concepts / History ER model, ER diagrams Relational model Relational algebra Relational calculus SQL Database Application Development