Database Reference
In-Depth Information
Figure 3.22
Table design of FACULTY_CLASS.
Figure 3.23
Table design of CLASS_CLASSROOM.
designs for the tables FACULTY_CLASS, CLASS, CLASS_CLASSROOM, and CLASSROOM
are given. he table design of FACULTY is given in Figure 3.12, the design of CLASSROOM is
given in Figure 3.10, and the design of CLASS is given in Figure 3.15.
A ternary relationship may not always be represented by a set of binary relationships. If this
happens, you may have to enforce constraints with programming in a database application.
At this point, you have done the irst two tasks, representing entities with relations and rep-
resenting relationships with primary key and foreign key pairs. he next task is to enforce con-
straints, discussed in the next section.
3.4.3 Enforcing Constraints
By using constraints, you will be able to implement relationships that link the tables in a database.
Constraints are widely used in a database to make sure that tables work together properly, so
modiications made in one table will not cause malfunctions in other tables. Constraints are also
used to verify data entered in a table to make sure that the data are in a proper format. here are
four types of commonly used constraints:
