Fuzzy Queries Based on EPTV in Relational Databases

Null values have different semantics in relational databases and influence the results of fuzzy queries.This paper distinguishes the different semantics of null values and attaches labels to these semantics.Relational operations and the complex nested queries are extended on the base of Extended Possibilistic Truth Values(EPTV) logic.Related definitions and calculation methods are proposed.Instances illuminate that the method can reflect the effects of different null values on query results compared with regular fuzzy queries.

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