Fastest way to determine if record exists

Question

As the title suggests... I\'m trying to figure out the fastest way with the least overhead to determine if a record exists in a table or not.

Sample query:

Answer 1

create or replace procedure ex(j in number) as
i number;
begin
select id into i from student where id=j;
if i is not null then
dbms_output.put_line('exists');
end if;
exception
   when no_data_found then
        dbms_output.put_line(i||' does not exists');

end;