Foundations of logic programming
Foundations of logic programming
On conjunctive queries containing inequalities
Journal of the ACM (JACM)
Optimization of real conjunctive queries
PODS '93 Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Containment of conjunctive queries: beyond relations as sets
ACM Transactions on Database Systems (TODS)
The complexity of querying indefinite data about linearly ordered domains
Journal of Computer and System Sciences - Special issue: dedicated to the memory of Paris Kanellakis
Equivalences Among Relational Expressions with the Union and Difference Operators
Journal of the ACM (JACM)
Database Management Systems
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
The containment problem for Real conjunctive queries with inequalities
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Database Systems: The Complete Book
Database Systems: The Complete Book
A secured collaborative model for data integration in life sciences
Transactions on large-scale data- and knowledge-centered systems IV
Classification of annotation semirings over query containment
PODS '12 Proceedings of the 31st symposium on Principles of Database Systems
Equivalence and minimization of conjunctive queries under combined semantics
Proceedings of the 15th International Conference on Database Theory
Classification of annotation semirings over containment of conjunctive queries
ACM Transactions on Database Systems (TODS)
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Conjunctive queries (CQs) are at the core of query languages encountered in many logic-based research fields such as AI, or database systems. The majority of existing work assumes set semantics but often in real applications the manipulation of duplicate tuples is required. One of the major problems that arises as part of advanced features of query optimization, data integration, query reformulation and many other research topics is testing for containment of such queries. In this work, we investigate the complexity of query containment problem for CQs under bag semantics (i.e. duplicate tuples are allowed in both the database and the results of queries) and under bag-set semantics (i.e. duplicates are allowed in the result of the queries but not in the database). We derive complexity results for these problems for five major subclasses of CQs; and we also find necessary conditions for CQ query containment. The general case of these problems remains open.