Question

So this is from a uni coursework and is my first time working with Oracle (and using triggers). We are supposed to be creating a database for an airlines.

Part of the database is

CREATE TABLE FLIGHT_BOOKING (
  BOOKING_ID NUMBER(11) PRIMARY KEY,
  BOOKING_TIME DATE NOT NULL,
  EMPLOYEE_ID NUMBER(11) NOT NULL,
  FLIGHT_ID NUMBER(11) NOT NULL,
  TOTAL_COST NUMBER(4,2) NOT NULL
);

CREATE TABLE FLIGHT (
  FLIGHT_ID NUMBER(11) PRIMARY KEY,
  PLANE_ID NUMBER(11) NOT NULL,
  START_ID NUMBER(11) NOT NULL,
  DESTINATION_ID NUMBER(11) NOT NULL,
  TRANSIT_ID NUMBER(11),
  DEPARTURE_TIME DATE NOT NULL,
  ARRIVAL_TIME DATE NOT NULL,
  NUM_BOOKED NUMBER (4) NOT NULL
);

CREATE TABLE PASSENGER (
  PASSENGER_ID NUMBER(11) PRIMARY KEY,
  FIRST_NAME VARCHAR2(20) NOT NULL,
  MIDDLE_NAME VARCHAR2(20) NULL,
  LAST_NAME VARCHAR2(20) NOT NULL,
  TELEPHONE NUMBER(11) NOT NULL,
  BOOKING_ID NUMBER(11) NOT NULL
);

So what I want to do is create a trigger such that every time a new passenger is added to the PASSENGER table, the trigger finds the corresponding FLIGHT_ID from the FLIGHT_BOOKING table and increments NUM_BOOKED for the corresponding flight in the FLIGHT table.

I have tried going through the oracle documentation, but i could not find anything that describes a situation where two or more tables are concerned.

Any help would be really appreciated!

Answer 1

you can do it like this:

CREATE OR REPLACE TRIGGER update_flight_booking_info
  AFTER INSERT ON PASSENGER
  FOR EACH ROW

DECLARE
    v_flight_id number;
    v_booking_id number;
BEGIN
    v_booking_id  := :new.booking_id ;

    select flight_id into v_flight_id
    from flight_booking
    where booking_id = v_booking_id;

    update flight
    set NUM_BOOKED = NUM_BOOKED + 1
    where flight_id = v_flight_id;
END;

HTH.