text: --test insert using self reference
  create class tb1(
  	col1 int,
  	col2 tb1
  );
  
  
  insert into tb1 values(1, null);
  insert into tb1 values(2, select tb1 from tb1 where col1=1);
  insert into tb1 values(3, select tb1 from tb1 where col1=2);
  
  select * from tb1;
  
  drop class tb1;
  