Constraint（一）

• not null與primary key

  • create table car
  • (cid character (10) constraint pk primary key,
  • model character(10) constraint nu not null,
  • price integer default 100
  • );
  • insert into car (price) values (100);
  • insert into car (cid,price) values ('c01',100);

• 設定Constraint可以避免輸入錯誤

• primary key 就是 not null且 unique