Project-Join Normal Form(PJNF) A relation schema R is in PJNF with respect to a set D of functional, multivalued,and join dependencies if for all join dependencies in D+ of the form *(R1,R2,...,Rn where each Ric R and R=RjUR2...UR at least one of the following holds: .*(R1,R2,...,R)is a trivial join dependency. Every R;is a superkey for R. Since every multivalued dependency is also a join dependency every PJNF schema is also in 4NF. Database System Concepts-7th Edition 28.9 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 28.9 ©Silberschatz, Korth and Sudarshan th Edition Project-Join Normal Form (PJNF) ▪ A relation schema R is in PJNF with respect to a set D of functional, multivalued, and join dependencies if for all join dependencies in D+ of the form *(R1 , R2 ,..., Rn ) where each Ri  R and R =R1 R2  ...  Rn at least one of the following holds: • *(R1 , R2 ,..., Rn ) is a trivial join dependency. • Every Ri is a superkey for R. ▪ Since every multivalued dependency is also a join dependency, every PJNF schema is also in 4NF