Question

I need help writing a MySQL trigger.

Suppose you have a student database with the following tables:

ENROLLMENT(SSN, CLASS_NO, GRADE)
CLASS(CLASS_NO, CLASS_TITLE, NO_OF_STUDENTS).

I need to write a trigger to increase the NO_OF_STUDENTS by one if a new student is added to the ENROLLMENT table for that CLASS_NO.

Answer 1

you can use mysql trigger to do this. Try something like

CREATE TRIGGER 'database_name'.'after_insert_enrollment' AFTER INSERT ON 'ENROLLMENT' 
FOR EACH ROW
BEGIN
UPDATE class SET NO_OF_STUDENTS = NO_OF_STUDENTS +1 WHERE CLASS_NO = NEW.CLASS_NO;
END