text: DROP TABLE region CASCADE;
  DROP TABLE nation CASCADE;
  DROP TABLE supplier CASCADE;
  
  create table region (
     r_regionkey int not null,
     r_name char(55) not null,
     r_comment char(152) not null,
     PRIMARY KEY ( r_regionkey )
  );
  
  create table nation (
     n_nationkey int not null,
     n_name char(25) not null,
     n_regionkey int not null references region(r_regionkey) ON DELETE CASCADE,
     n_comment char(152) not null,
     PRIMARY KEY ( n_nationkey )
  );
  
  create table supplier (
     su_suppkey int not null,
     su_name char(25) not null,
     su_address varchar(40) not null,
     su_nationkey int not null references nation(n_nationkey) ON DELETE CASCADE,
     su_phone char(15) not null,
     su_acctbal numeric(12,2) not null,
     su_comment char(101) not null,
     PRIMARY KEY ( su_suppkey )
  );
  