?? rel-ops.txt
字號:
1.
SELECT Title, Price
FROM BOOK
WHERE PublisherID IN (SELECT PublisherID
FROM PUBLISHER
WHERE Name = 'Electronics Industry' OR Name = 'NWPU Press');
2.
SELECT Name
FROM Publisher
WHERE PublisherID IN (SELECT PublisherID
FROM Book
WHERE Book.title = 'Database Systems');
I used select relational operation, which can return the special colomn of the table.
I select the price and title from the table book when its PublisherID is selected in the table publisher whose name is 'Electronics Industry' or 'NWPU Press'.
I use the same relational operation to know a publisher which has special book.
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