text: --create class and alter classs by adding some attributes and droping two attributes in one time
  
  CREATE CLASS ddl_0001;
  
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col1  integer;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col2  varchar(100) nOt nUlL unique;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col3  varchar(100) unique NOT NULL;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col4  varchar(100) default 'hello' NoT NuLl;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col5  varchar(100) default 'hello' not null;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col6  numeric(10,5);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col7  numeric(10,5);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col8  numeric(10,5);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col9  integer;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col10 integer;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col11 char(10);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col12 char(10);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col13 numeric(10);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col14 numeric(10);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col15 char(10);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col16 char(10);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col17 char(10);
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col18 timestamp;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col19 timestamp;
  ALTER CLASS ddl_0001 ADD ATTRIBUTE col20 timestamp;
  
  
  ALTER CLASS ddl_0001 drop attribute col20, col17;
  ALTER CLASS ddl_0001 drop col13, col11;
  ALTER ddl_0001 drop col8, col1;
  
  
  
  
  drop class ddl_0001;