?? rel-ops.txt
字號:
1
SELECT Title,Price
FROM BOOK
WHERE PublisherID IN (SELECT PublisherID
FROM PUBLISHER
WHERE Name = "Thomas Connolly" OR Name = "Lippman");
2
SELECT Name
FROM PUBLISHER, BOOK
WHERE PublisherID IN (SELECT PublisherID
FROM BOOK
WHERE 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 "Thomas Connolly" or "Lippman".
I use the same relational operation to know a publisher which has special book,select the Name from the table PUBLISHER when its PUBILSHERID is selected in the table BOOK,whose Title is "Database Systems".
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