Cloud Database Development and Management

250  ◾  Cloud Database Development and Management

7.4.2 Using Triggers

Now, we will discuss how triggers are used in database management and business logic imple-

mentation through examples. Triggers will be used to enforce business constraints and implement

application logic dynamically to keep database integrity.

7.4.2.1 Validating Business Constraints

Here, we will use a trigger to verify if a student has met the prerequisite requirement before he/she

enrolls in a new class. Before a student and class information can be added to the table STUDENT_

CLASS, an AFTER trigger is used to query the courses that have been taken by the student and

then compare the prerequisite of the course to be taken. If there is a match, add the student and

class ...