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Editorial Team
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Asked: 2026-05-26T18:46:03+00:00

so I am creating an oracle database for my university coursework on an airline.

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so I am creating an oracle database for my university coursework on an airline. Now i have a table called staff_allocations which allocate staff for flights in the Flight table. 

CREATE TABLE FLIGHT (
  FLIGHT_ID NUMBER(11) PRIMARY KEY,
  ROUTE_ID NUMBER(11) NOT NULL,
  PLANE_ID NUMBER(11) NOT NULL,
  PILOT_ID NUMBER(11) NOT NULL,
  DEPARTURE_TIME TIMESTAMP NOT NULL,
  ARRIVAL_TIME TIMESTAMP NOT NULL,
  FREE_SEATS NUMBER (4)
);

CREATE TABLE STAFF_ALLOCATION (
    FLIGHT_ID NUMBER(11) NOT NULL,
    EMPLOYEE_ID NUMBER(11) NOT NULL
);

now the route_id in the flight table references the routes table.

CREATE TABLE ROUTE (
  ROUTE_ID NUMBER(11) PRIMARY KEY,
  START_ID VARCHAR2(3) NOT NULL,
  DESTINATION_ID VARCHAR2(3) NOT NULL,
  TRANSIT_ID VARCHAR2(3),
  IS_ACTIVE VARCHAR2(1),
  DISTANCE NUMBER (8,2),
  BASE_PRICE NUMBER (6,2)   
);

where start id, destination id and transit id all point to different airport codes (LHR, HAM, etc.)

so i am trying to make a trigger that will figure out before insert on staff_allocation, whether the staff is allocated to another flight whose time overlaps with the new one. also, it has to check whether the staff is actually in the same country as the origin of the flight.

so something like this :

find which flights staff member is allocated to already.
compare new flight departure time to existing flight departure times.
if flight times don’t clash, then see if staff is already in the country of the new start_id

can anyone help me out with either example code or by pointing me in the right direction in what i should be looking at/using? this is my first time at creating anything with oracle.

cheers.

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1 Answer

  1. Editorial Team

    The first check is quite easy. If you know the departure and landing of the flight you are modifying, you can check if there exists another flight for the employee, of which the arrival datetime is greater than the departure date of the current flight, and the departure datetime of that flight is before the arrival date time of the current flight.

    If such a flight exists, it overlaps with your current flight. But this is more logic that Oracle.

    The other check is harder (for a database). You will have to find the latest arrival for a specific employee and choose the country of arrival as the country in which the employee arrives.
    Note that this is hypothetical. Someone could have gone home as a passenger, or by bus. Also, you will need to make sure you have a starting point for each employee. So either you will have to allow everything for someone’s first flight, or you will have to register the country with the employee itself. The latter solution doesn’t ‘time travel’ very well, it is only a fixed location, and it doesn’t tell where the employee will be on a certain date. So I would just allow any allocation for employees that are new, and don’t bother about the rest for this assignment.

    The main problem you’re going to face, is that you cannot query a table in a row level trigger on that same table. So for this to work out, you will have to remember the inserted records and write a table level after insert trigger to do the checking.

    I’d love to give you some code, but people keep telling me that students should do their own. So I’ll leave the implementation to you, while I’m going to do my own homework. 🙂

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