A sequence number error in a form

Question

I am currently creating a form with a sequence number in forms 10g
<pre>
table name: emp
table desc: emp_id number,emp_name varchar2(20),emp_no number
</pre>
i have to generate the emp_id automatically.
<pre>
create sequence emp_seq
minvalue 1
start with 1
increment by 1
cache 20
</pre>
I use pre_insert trigger in block
<pre>
begin
select emp_seq.nextval into :emp.emp_id from dual
end
</pre>
problem;
I can not insert a record because of sequence number in :emp.emp_id
no compilation error but there is no automatic sequence number appeared in :emp.emp_id after run a form.
It used to work before(fine with automatic sequence number in :emp.emp_id).
it happens after I changed layout format and someone add more columns in emp table.
eventhough i did not use sequence number in emp.emp_id
in pre-insert-trigger
<pre>
begin
select nvl(max(emp_id),0)+1
into :emp.emp_id
from emp;
</pre>
still can not show up any number in :emp.emp_id
please help me out

Answer 1

Thank you . It works now.
would you mind explain to me; what I can not use automatic sequence number in emp.empid text field in pre-insert-trigger in my case
is it trigger confliction in my forms?