Pl Pgsql problem

Hi,

I am using 7.1.3 on RedHat Linux 7.2.

I try to create a trigger on the table, I wrote a function in plpgsql, which always fail on this sql command:

select (''UPD'' || int2hex(nextval(''updid''), 8)) as v_updid;

The function is like this:

begin

            select (''UPD'' || int2hex(nextval(''updid''), 8)) as v_updid;

            if not found then

                 raise exception ''Unable to get updid.'';

            end if;

        end;

It give me this error when I trigger the function:

NOTICE:  Error occurred while executing PL/pgSQL function pg_fct_bf_ins_inf_article

NOTICE:  line 9 at SQL statement   -- the SQL select command

ERROR:  parser: parse error at or near "$1"

I can execute the SQL without problem.

<<

select ('UPD' || int2hex(nextval('updid'), 8)) as v_updid;

>>

Can anyone help me to see what is the problem here.

Li Hao