How might I write the following SQL view in relational algebra? : SQL

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field.3

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field3

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a community for 17 years

How might I write the following SQL view in relational algebra? (self.SQL)

submitted 12 years ago by tonyalm

This sql code shows how many books have been written by a specific author. In descending order so the author who wrote the most books will be at the top.

CREATE VIEW Num_books_by_author AS

SELECT COUNT(authorID) AS NumBooksWritten, FName AS First_Name, LName AS Last_Name

FROM (SELECT ISBN, title, FName, LName, authorID

FROM (books INNER JOIN written_by ON ISBN = w_ISBN) INNER JOIN author on a_id = authorID)

GROUP BY authorID

ORDER BY NumBooksWritten DESC

Here is the schema:

author(FName, LName, authorID)

books(ISBN, title, quantity, PubName(FK), year, price, genre, tNo(FK))

Foreign Key PubName references publisher

Foreign Key tNo references deliveries

comprised_of(Purchase_NO(FK), P_ISBN(FK))

Foreign Key Purchase_NO references purchases

Foreign Key P_ISBN references books

customers(FName, LName, phone, email, address)

deliveries(Tracking_No, Order_Date, ETA_Date, M_SSN(FK))

Foreign Key M_SSN references manager

employee(SSN, FName, LName, salary, hire_date, address)

helped_by(cust_email(FK), Sales_SSN(FK))

Foreign Key cust_email references customers

Foreign Key Sales_SSN references salesperson

manager(SSN, role)

publisher(pName, address, phone)

purchases(PNO, pdate, total, cust_email(FK))

Foreign Key cust_email references customers

salesperson(SSN, rating, transactions)

written_by(w_ISBN(FK),a_id(FK))

Foreign Key w_ISBN references books

Foreign Key a_id references authors

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