text: -- create class using primary key on varchar data type
  
  create class aoo ( a varchar(10) primary key, b int, c int );
  
  select attr_name, is_nullable from db_attribute where class_name = 'aoo' order by 1,2;
  
  select * from db_index where class_name = 'aoo';
  
  select * from aoo;
  
  drop aoo;