rel-ops.txt

ssd7 练习一答案 供大家参考 如有错误 请多多包涵

(
	select Book.title, Book.price
	from   Book, PUBLISHER
	where  Book.PublisherID = PUBLISHER.PublisherID and PUBLISHER.PublisherName = 'MIT Press'
)
union
(
	select Book.title, Book.price
	from   Book, PUBLISHER
	where  Book.PublisherID = PUBLISHER.PublisherID and PUBLISHER.PublisherName = 'University of Chicago Press'
);

use select adn join operations.

In order to search books published by MIT Press and University of Chicago Press, then print them in title and price.

Union operation can join this two select together.