[SQL] plpgsql ?

[guard]

Hi all,

i have a question 'plpgsql'

my code

CREATE FUNCTION autono (text,text) RETURNS text AS '
  DECLARE
    a1 ALIAS FOR $1;
    a2 ALIAS FOR $1;
    ret_val text;
  BEGIN
    select tna  into ret_val from a1  where pamt_no=a2;

  RETURN ret_val;
END;' LANGUAGE 'plpgsql'


error run  "   select tna  into ret_val from a1  where pamt_no=a2;    "
help me ,thanks