Traditional set operations include

Traditional set operations include four operations: union, difference, intersection and cartesian product.

1) union

The union of relation R and relation S is marked as:, and the result is still an n-mesh relation, which consists of tuples belonging to R but not S.

(2) except

The difference between relation R and relation S is recorded as:, and the result is still an n-mesh relation, which consists of all tuples belonging to R but not S.

(3) intersection

The intersection of relation R and relation S is marked as:, and the result is still an n-mesh relation, which consists of tuples belonging to both R and S. The return of the relation can be expressed by the difference: R∩S=R-(R-S).

(4) cartesian product

the elements of cartesian product are tuples. The Cartesian products of two relations R and S with N-mesh and M-mesh respectively are a set of tuples with an (n+m) column. If R has K1 tuples and S has K2 tuples, the Cartesian products of R and S have K1×K2 tuples.