Creating a row trigger to populate the primary key

Question

to populate the primary key of a table automatically, i created a sequence named rule_id
using the following statement:
create sequence rule_id;
and then i created a trigger to populate the primary key using the statements below:
CREATE OR REPLACE
TRIGGER RULE_ID BEFORE INSERT ON DOC_CATS_RULE_BASED_CLASS
FOR EACH ROW
BEGIN
SELECT SEQ_RULE_BASED_CLASS.NEXTVAL
INTO :new.id FROM DUAL;
END;
i took this from a books example. but it gives and error called:
Error(3,8): PLS-00049: bad bind variable 'NEW.ID'
What is wrong and what is the current way to do it?
Please help!

Answer 1

Hi ,
The new denotes the new data values for the table relative column.....
As regards the dual is a small table in the data dictionary that Oracle and user-written programs can reference to guarantee a known result. This table has one column called DUMMY and one row containing the value X.
Regards,
Simon