postgresql触发器记录表记录的更改

SELECT * INTO card_record FROM card where false;
alter table card_record add time numeric;
alter table card_record add flag character(1);

CREATE OR REPLACE FUNCTION record_card()
  RETURNS trigger AS
$BODY$
begin
    if(TG_OP='INSERT')then
        insert into card_record select NEW.*,EXTRACT(EPOCH from current_timestamp(0)),'I';
    elseif(TG_OP='DELETE')then
        insert into card_record select OLD.*,EXTRACT(EPOCH from current_timestamp(0)),'D';
    elseif(TG_OP='UPDATE')then
        insert into card_record select OLD.*,EXTRACT(EPOCH from current_timestamp(0)),'U';
    end if;
return null;
end;
$BODY$
  LANGUAGE 'plpgsql';

CREATE TRIGGER trig_record_card
  AFTER INSERT OR UPDATE OR DELETE
  ON card
  FOR EACH ROW
  EXECUTE PROCEDURE record_card();