text: -- create class attribute using default constraints
  
  create class picture
  (caption set string,
   image string);
   
   insert INTO picture VALUES ({'s'},'s');
   
   create class meal
  class attribute (meal_type string default 'a')
  (menu picture);
   
   select * FROM db_attribute WHere class_name='meal' order by 1;
   
   SELECT picture INTO a FROM picture where image='s';
   
   INSERT INTO meal VALUES (a);
   
   SELECT * FROM meal;
   
   
   DROP picture;
   
   DROP meal;
  