The PROJECT operation
The project operation is used to choose the records with specified attributes as discarding the others based on some related criteria. This is denotes as ∏
Consider the relation PERSON. If you want to display only the names of persons then the project operation will be used as follows:
Π Name (PERSON)
The resultant relation will be as follows:
1) Π ( Π (R))= Π (R)
As long as have attributes in .