Incomplete Information in Relational Databases
Journal of the ACM (JACM)
Journal of Computer and System Sciences
Relational database writings (1985–1989)
Relational database writings (1985–1989)
On the representation and querying of sets of possible worlds
Selected papers of the workshop on Deductive database theory
Formal semantics of SQL queries
ACM Transactions on Database Systems (TODS)
A foundation of CODD's relational maybe-operations
ACM Transactions on Database Systems (TODS)
On semantic issues connected with incomplete information databases
ACM Transactions on Database Systems (TODS)
Extending the database relational model to capture more meaning
ACM Transactions on Database Systems (TODS)
Null values in data base management a denotational semantics approach
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
Information and Software Technology
Consistency enforcement in databases
Proceedings of the 2nd international conference on Semantics in databases
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Some problems connected with the handling of null values in SQL are discussed. A definition of sure answers to SQL queries is proposed which takes care of the “no information” meaning of null values in SQL. An algorithm is presented for modifying SQL queries such that answers are not changed for databases without null values but sure answers are obtained for arbitrary databases with standard SQL semantics.