text: -- create subclass with fk from superclass having Foreign key
  
  create table p7 (a int primary key, b int);
  create table p1 (b int , a int,FOREIGN KEY (a) REFERENCES p7(a));
  create TABLE p2 UNDER p1 (c int, FOREIGN KEY (c) REFERENCES p7(a));
  
  select attr_name, is_nullable from db_attribute where class_name = 'p2' 
  order by 1,2;
  
  select * from db_index where class_name = 'p2' order by 1,2;
  
  select * from p2 order by 1,2;
  
  drop p2;
  drop table p1;
  drop table p7;