Treat

create table Treat(
  Did int references Doctor(Did) on delete cascade,
  Pid int references Patient (Pid) on delete set null,
  Diagnosis varchar(30) not null,
  treat_id int,
  treat_date date
);
insert into Treat values('D_100', 'XYZ', 'ENT', 12334, 150);
insert into Treat values('D_101', 'PQR', 'ORTHO', 12455, 200);
insert into Treat values('D_102', 'LMN', 'ENT', 12256, 150);
insert into Treat values('D_103', 'ABC', 'GEN.MED', null, 150);
insert into Treat values('D_106', 'KLM', 'PEDIATRIC', 12987, 200);
insert into Treat values('D_104', 'JACK', 'CARDIAC', 13567, 200);