CREATE TABLE OBJECT (
       ID BIGINT NOT NULL,
       PARENTID BIGINT,
       CONSTRAINT PK_OBJECT PRIMARY KEY (ID)
);
ALTER TABLE OBJECT ADD CONSTRAINT FK_OBJECT_1 FOREIGN KEY (PARENTID) REFERENCES OBJECT(ID);

CREATE PROCEDURE ROOT (ID BIGINT)
returns (ROOTID BIGINT)
AS 
  declare variable ParentID BigInt;
begin
for select ParentID from object where (ID=:ID) into :ParentID do
begin
  if (ParentID is NULL) then
  begin
    RootID = ID;
    suspend;
  end else
  begin
    for select RootID from Root(:ParentID) into :RootID do
    begin
      suspend;
    end
  end
end
end

select ID, ParentID, RootID from object
left join Root(ID) on ID=ID