Review 2: of Relational Algebra Set operations:Union,intersection and difference (the relation schemas must be the same) ■ Selection:Picking certain rows from a a relation. Projection:picking certain columns. Products and joins:composing relations in a useful ways. ■ Renaming of relations and their attributes.Review 2: “Core” of Relational Algebra „ Set operations: Union, intersection and difference (the relation schemas must be the same) „ Selection: Picking certain rows from a relation. „ Projection: picking certain columns. „ Products and joins: composing relations in a useful ways. „ Renaming of relations and their attributes