The algebra on sets of tuples or relations could be used to express typical queries about those relations (1) Union (2) set difference (3) Cartesian Product (4) selection
(5) projection (6) aggregation (7) renaming
set operation(union, intersection, difference), selection, projection, Cartesian product, natural join, theta-join, renaming, duplicated elimination, aggregation, grouping, sorting, extended projection,outerjoin (naturla, left, right)
Intersection, theta join, natural join are dependent operations.
Union, differences, production, selection, projection, renaming are independent operations
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