主键约束
create table Items(ItemNo number(2) constraint PK_Items primary key,
ItemName varchar2(20) not null);
外键约束
create table business(
busino number(2) constraint pk_business primary key,
businessname varchar(32) not null,
itemno number(2) ,
constraint fk_business foreign key(itemno) references Items(ItemNo),
starttime date
);
