Help with Relational Algebra

[scorpiomailin]

Hello Guys...
thanks in advance jst wondering if any1 knows answer to this....
if this is the SQL query

Author(name, hometown, publisher)
Textbook(tname, aname, price)
select A.name, publisher from Author A, Textbook T
where T.aname = A.name and not exists (select * from Textbook S
where S. price > T.price);


What would be an efficient relational algebra????? so that there are minimal tuples to be processed...

[MMcCarthy]

Author(name, hometown, publisher)
Textbook(tname, aname, price)

SELECT A.name, A.publisher
FROM Author A INNER JOIN Textbook T
ON A.name=T.aname
WHERE T.aname not exists (select S.aname from Textbook S
where S.price > T.price);

This would be your query but it doesn't make sense, you're taking price from the same table both times. What are you trying to do?