to create an trigger in pl/sql

i have a problem that i want to create an trigger t开发者_开发问答hat checks the Pincode number is exactly six of digit or not.

please tell me an detail answer.

I suppose you mean a character column in your question, if so - you can achieve this without trigger but using check constraint like this:

create table test_1
(
pincode varchar2(20)
  constraint test_1$chk$id check (ltrim(pincode, '0123456789') is null and length(pincode)= 6)
);

Running these inserts:

insert into test_1 (pincode) values ('45sdgf65');
insert into test_1 (pincode) values ('4565');

Will result the error:

ORA-02290: check constraint (ANDREW.TEST_1$CHK$ID) violated

But this one goes ok:

insert into test_1 (pincode) values ('034565');