Using Multivalued Logic in Relational Database Containing Null Value

In this paper, several kinds of multivalued logic for relational database and their developing process are presented on the basis of null value's semantics. A new 5 valued logic is led into relational database containing null talue. The feasibility and necessity of using 5 valued logic are expounded. Comparative calculation and logical calculation under 5 valued logic are defined at the end of the paper.