Selection, [σ], selects rows from a table. Example: σ Firstname = ‘Thibault’(STUDENT)
Projection, [π], projects out columns from a table. Example: π Firstname(STUDENT)
Renaming, [ρ], can be used to rename tables. Example: ρ Firstname <- Name(STUDENT)
Cartesian product, [x], of two relations (tables) consists of all the tuples of the first, combined in all possible ways with the tuples of the second. Example: A x B = {< a,b >: for all a,b aEA and bEB}
Natural Join, [∞], matches up corresponding attributes (attributes with the same names and values) in two tables. The result is a table in which no two attributes have the same name. Example: Employee ∞ Department
Division, [%], restricts attributes names uniqueness of a table, for which it holds that all their combinations with another table are present in the first one. Example: Employee % Department
Union, [∪], of a collection of sets is the set of all distinct elements in the collection. Example: A ∪ B = {x: xEA or xEB}
Intersection, [∩], of two sets A and B is the set that contains all elements of A that also belong to B but no other elements. Example: A ∩ B = {x: xEA and xEB}
Set Difference, [\], of U and A (U\A) is the set of all members of U that are not members of A (also called relative complement) Example: U\A = {xEU | x!EA}