Consider the database shown in Figure 1.2, whose schema is shown in Figure 2.1. What are the referential integrity constraints that should hold on the schema? Write appropriate SQL DDL statements to define the database.

Question

What will be an ideal response?

Answer 1

The following referential integrity constraints should hold (we use the notation: R.(A1, ..., An) --> S.(B1, ..., Bn)
to represent a foreign key from the attributes A1, ..., An of R (the referencing relation)
to S (the referenced relation)):
PREREQUISITE.(CourseNumber) --> COURSE.(CourseNumber)
PREREQUISITE.(PrerequisiteNumber) --> COURSE.(CourseNumber)
SECTION.(CourseNumber) --> COURSE.(CourseNumber)
GRADE_REPORT.(StudentNumber) --> STUDENT.(StudentNumber)
GRADE_REPORT.(SectionIdentifier) --> SECTION.(SectionIdentifier)
One possible set of CREATE TABLE statements to define the database is given below.
CREATE TABLE STUDENT ( Name VARCHAR(30) NOT NULL,
StudentNumber INTEGER NOT NULL,
Class CHAR NOT NULL,
Major CHAR(4),
PRIMARY KEY (StudentNumber) );
CREATE TABLE COURSE ( CourseName VARCHAR(30) NOT NULL,
CourseNumber CHAR(8) NOT NULL,
CreditHours INTEGER,
Department CHAR(4),
PRIMARY KEY (CourseNumber),
UNIQUE (CourseName) );
CREATE TABLE PREREQUISITE ( CourseNumber CHAR(8) NOT NULL,
PrerequisiteNumber CHAR(8) NOT NULL,
PRIMARY KEY (CourseNumber, PrerequisiteNumber),
FOREIGN KEY (CourseNumber) REFERENCES
COURSE (CourseNumber),
FOREIGN KEY (PrerequisiteNumber) REFERENCES
COURSE (CourseNumber) );
CREATE TABLE SECTION ( SectionIdentifier INTEGER NOT NULL,
CourseNumber CHAR(8) NOT NULL,
Semester VARCHAR(6) NOT NULL,
Year CHAR(4) NOT NULL,
Instructor VARCHAR(15),
PRIMARY KEY (SectionIdentifier),
FOREIGN KEY (CourseNumber) REFERENCES
COURSE (CourseNumber) );
CREATE TABLE GRADE_REPORT ( StudentNumber INTEGER NOT NULL,
SectionIdentifier INTEGER NOT NULL,
Grade CHAR,
PRIMARY KEY (StudentNumber, SectionIdentifier),
FOREIGN KEY (StudentNumber) REFERENCES
STUDENT (StudentNumber),
FOREIGN KEY (SectionIdentifier) REFERENCES
SECTION (SectionIdentifier) );