3.21 考虑图3-21中的图书馆数据库。用SQL写出如下查询:
member(memb_no, name, age)
book(isbn, title, authors, publishers)
borrowed(memb_no, isbn, date)
图3-21 习题3.21的图书馆数据库
为了解题方便,在数据库中创建这些关系:
create table member (
memb_no varchar,
name varchar,
age int,
primary key (memb_no)
);
create table book(
isbn varchar,
title varchar,
authors varchar,
publishers varchar,
primary key (isbn)
);
create table borrowed (
memb_no varchar,
isbn varchar,
date varchar,
primary key (memb_no, isbn),
foreign key (memb_no) references member on delete no action,
foreign key (isbn) references book on delete no action
);
insert into member values ('会员号_1', '会员_1', 18);
insert into member values ('会员号_2', '会员_2', 19);
insert into memb