Database Reference
In-Depth Information
Table 2.8
Summary of Relationships
Relationship
Type
Related Entities
Cardinality
Course—Class
Nonidentifying
COURSE
CLASS
One course is related to
one or more classes
Course—
Prerequisite
Many-to-many
recursive
COURSE
COURSE_
PREREQUISITE
One or more courses are
related to zero or more
prerequisites and vice versa
Weekday—Class
Nonidentifying
DAYS
CLASS
One weekday is related to
zero, one, or more classes
Time
Block—Class
Nonidentifying
TIMEBLOCK
CLASS
One time block is related to
zero, one, or more classes
Semester—Class
Nonidentifying
SEMESTER
CLASS
One semester is related to
one or more classes
Faculty—Student
Nonidentifying
FACULTY
STUDENT
One faculty advisor is
related to zero, one, or
more students
Building—
Classroom
Identifying
BUILDING
CLASSROOM
One building is related to
one or more classrooms
Class—Student
Class—
Classroom
Class—Faculty
Many-to-many-
to-many
N
-ary
STUDENT
CLASS
CLASS_STUDENT
CLASSROOM
CLASS_
CLASSROOM
FACULTY
CLASS_FACULTY
At least 10 students are
related to 0-7 classes, zero
or more instructors, and
one or more classrooms
and vice versa
intersection entity CLASS that contains the attributes CourseID, DayID, TimeID, and
SemesterID. However, as shown in later chapters, by doing so, this will make the inter-
section entities for the many-to-many relationships Class-Student, Class-Classroom, and
Class-Faculty include all the attributes in the entity CLASS, which will cause a large num-
ber of redundancies.
Some of the relationships in Table 2.8 have been deined before. he Course-Class rela-
tionship is deined in Figure 2.15. he Course-Prerequisite relationship is deined in Figure
2.12. he Faculty-Student relationship for advising is deined in Figure 2.18. he Building-
Classroom relationship is deined in Figure 2.17. he
N
-ary relationship can be represented
by multiple binary relationships shown in Figure 2.19.
