Move/fetch cursor in loop (PostgreSQL) -

i need create trigger check if new inserted element's id isn't repeated. problem in loop statement, console spit out error:

context:  sql statement in pl/pgsql function "foo" near line 7 line 1: move forward 1  $1 

here function:

create function foo() returns trigger as' declare xyz cursor select id accounts;      begin         loop             if new.id = xyz                 raise notice ''id used!'';             else                 move forward 1 xyz;             end if;         end loop;     return new;     close xyz;     end; ' language 'plpgsql';  create trigger foo before insert on accounts each row execute procedure foo(); 

your example has no sense (you can't compare scalar value cursor). cursor self pointer without value.

   if new.id = xyx 

why don't do

 begin   if exists(select * accounts a.id = new.id)     raise notice ''id used''; -- better raise exception   end if;   return new; end; 

second nonsense

   return new;   close xyz; -- no statement executed after return