Need help creating trigger with delete capabilities

Question

I have two tables:
create table person(userid integer,
lname varchar(20),
fname varchar (20),
phone_number varchar(12),
email_address varchar(35),
city varchar(20),
zip_code varchar(20),
department varchar(20),
major_street varchar(20),
cross_street varchar(20),
notes varchar(100),
Primary Key (userid));
create table vehicle(car_id integer,
make varchar(15),
model varchar(20),
year integer,
gas_mileage integer,
capacity integer,
owner integer,
primary key (car_id),
foreign key (owner) references person (userid));
I am trying to create a trigger that would delete all those records in vehicle whenever someone deletes a record in the person table. Here is the code that I run but it get a compilation error. Here is the the trigger text followed by the error:
CREATE OR REPLACE TRIGGER ON_DELETE_PERSON
AFTER DELETE ON person FOR EACH ROW
BEGIN
DELETE from vehicle
where owner=userId;
END;
2/4 PL/SQL: SQL Statement ignored
3/19 PL/SQL: ORA-00904: "USERID": invalid identifier
Any suggestions?

Answer 1

CREATE OR REPLACE TRIGGER ON_DELETE_PERSON
BEFORE DELETE ON person FOR EACH ROW
BEGIN
DELETE from vehicle
where owner=:old.userId;
END;