--創建設備信息表
create table device_info_tab
(device_code varchar2(24) not null ,
 device_name varchar(24) not null,
 description varchar(1000) null,
 oper_date date not null,
 buyer varchar2(24) null,
 lend_status integer null
     check(lend_status in(0,1)),
 lend_id integer null);
 --添加設備編號主鍵
 alter table device_info_tab
  add(primary key(device_code));

--創建設備借出信息表
create table device_lend_info_tab
(lend_id integer not null, 
 device_code varchar2(24) not null,
 borrower varchar(24) not null,
 borrow_date date null,
 return_date date null
 );
 --添加借出id主鍵
 alter table device_lend_info_tab
 add (primary key (lend_id));
 --添加設備編號外鍵
 alter table device_lend_info_tab
 add(foreign key(device_code) references device_info_tab);
 --創建可以遞增的序列號供lend_id使用
 create sequence seq_lend_id increment by 1 start with 1
 nomaxvalue nominvalue nocycle;