how to call sequence in oracle form6i?

[Rohullah]

hello

How to call sequence in oracle form6i.

i call it by this way it give Error.

i create Sequence with the name (St_seq)

and i call it ON WHEN-BUTTON-PRESS TRIGGER
as following.

begin
select st_seq.nextval into :student.sid from dual;
end;

give me the best answer.

thank you in advance.