create or replace function IncreaseTicketPrice()
returns trigger as $$
declare
    BaggagePrice decimal;
begin
    select price
    into BaggagePrice
    from baggagetype
    where id = new.baggagetypeid;

    update ticket
    set finalprice = finalprice + BaggagePrice
    where id = new.ticketid;

    return new;
end;
$$ language plpgsql;

create trigger TicketPriceIncrease
after insert on baggage
for each row execute function IncreaseTicketPrice();