Cloud Database Development and Management

260  ◾  Cloud Database Development and Management

3. To verify that the trigger prevents a class not listed in table CLASS from being entered

in the table STUDENT_CLASS, enter the following SQL statement to insert the class

1007 for the student with the id 10:

INSERT INTO STUDENT_CLASS

VALUES (10, 1007, NULL)

4. Highlight the code and click Run. As shown in Figure 7.31, the trigger Class_Checking

prevents the class 1007 from being entered to the STUDENT_CLASS table because it

is not listed in the CLASS table.

5. In contrast, if a class does exist in the CLASS table, the trigger will allow it to be

inserted to the STUDENT_CLASS table (Figure ...