Yet another bad bind variable in triggers

Question

getting a bad bind variable "old.seatsremain" and "new.seatsremain". Trying to make this trigger automatically decrease the number of seats for the offering if the seats are available for the particular offering. Do I have to declare all the variables with the : in front of it???? my two tables are:

enrollments
{sid number,
offerno number;)

and

offering
{offerno number,
courseno varchar2(10),
instructor varchar2(10),
seatsremain number;}

UPDATED CODE TESTING: OK so I incorporated the coding Fumble gave me and it cleared the errors for ones that originally popped up however I tested out this new code and I still have some remaining error because of the EXCEPTION clause which I have no idea why because the syntax I double checked should be right. any ideas??

create or replace trigger enroll_bef_ins_row
before insert on enrollments
for each row
declare
    originstruct    offering.instructor%type;
    origcourseno    offering.courseno%type;
    original    offering.seatsremain%type;
    seatsremain_already_full    exception;
begin
    Select seatsremain, instructor, courseno into original, originstruct, origcourseno from offering where offerno= :new.offerno;
    if original > 0 then
        update offering set seatsremain= seatsremain - 1;
        dbms_output.put_line ('Seats available in offering'||offerno||'have decreased from'||original|| 'to' ||(seatsremain));
    else if original = 0 then
        raise seatsremain_already_full;
        dbms_output.put_line ('Offering'||offerno||'is already full!');
    else
        update offering set offerno = :old.offerno;
        update offering set courseno = origcourseno;
        update offering set instructor = originstruct;
        update offering set seatsremain = original;

    end if;

exception
    when seatsremain_already_full then
        raise_application_error (-20001, 'Cannot allow insertion');
commit;
end;
/

THIS ERROR SHOWS UP NOW: PLS-00103: Encountered the symbol "EXCEPTION" when expecting one of the following: begin case declare end exit for goto if loop mod null pragma raise return select update while with << close current delete fetch lock insert open rollback savepoint set sql execute commit forall merge pipe

PLS-00103: Encountered the symbol "end-of-file" when expecting one of the following: end not pragma final instantiable order overriding static

Answer 1

You are using correlation names from a table other than the one your trigger is created for. Try declaring oldSeatsRemain and NewSeatsRemain as variables within your trigger.

Try this (note: this sample has not been executed). It includes the edits I described in my comments.

    create or replace trigger enroll_bef_ins_row
    before insert on enrollments
    for each row

    declare
        offerrow offering%rowtype;
        seatsremain_already_full    exception;
        pragma autonomus_transaction;
    begin
        Select seatsremain into offerrow from offering where offerno= :new.offerno;
        if offerrow.seatsremain > 0 then
            update offering set seatsremain= offerrow.seatsremain - 1;
            dmbs_output.put_line ('Seats available in offering ' |offerno| ' have decreased from ' |offerrow.seatsremain| ' to ' |offerrow.seatsremain-1|);
        else if original = 0 then
            dbms_output.put_line ('Offering ' |offerno| ' is already full!');
            raise seatsremain_already_full;
        else
            insert into offering
            values(offering.offerno,offering.courseno,offering.instructor,offering.seatsremain);
        end if;
        commit;
    exception
        when seatsremain_already_full
        raise_application_error (-20001, 'Cannot allow insertion');
    end
    /