Constraint（二）

• primary key的另一種寫法：

  • create table service
  • (sid integer,
  • name character (20) default '菜鳥廠商',
  • area character (6),
  • tel character (16),
  • addr character (50) constraint snu unique,
  • primary key (sid)
  • );

• unique 限制不重複

  • insert into service (sid,addr) values('5','台灣');
  • insert into service (sid,addr) values('6','台灣');