我的数据库类有一个项目,可以为一组库创建一个数据库。我正在使用 MySQL 5.2。我必须编写一个查询来查找保存每本书副本的两个图书馆。这些是创建表语句
Create table books(
booknum VARCHAR (10),
btitle VARCHAR (),
bpages SMALLINT,
bcdate DATE,
primary key (booknum))
Create table copies(
cnum VARCHAR(12),
cprice DECIMAL (7,2),
cpurdate DATE,
booknum VARCHAR(10),
primary key (cnum),
foreign key (booknum)
references book(booknum))
Create table library(
libnum VARCHAR(7),
libname VARCHAR (40),
streetNumber VARCHAR (8),
streetName VARCHAR (20),
city VARCHAR (20),
state VARCHAR (2),
zipcode VARCHAR (5),
primary key (libnum))
我相信我需要一个类似的东西
SELECT libname FROM libraries WHERE NOT EXISTS
(SELECT * FROM copies C, books B WHERE C.booknum=B.booknum)
但这不是吗?