On conjunctive queries containing inequalities
Journal of the ACM (JACM)
Principles of database and knowledge-base systems, Vol. I
Principles of database and knowledge-base systems, Vol. I
Minimizing restricted-fanout queries
Discrete Applied Mathematics - Special issue on combinatorial problems in databases
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)
Semantic query optimization in Datalog programs (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
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
An overview of query optimization in relational systems
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Rewriting aggregate queries using views
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
On optimizing an SQL-like nested query
ACM Transactions on Database Systems (TODS)
Efficient optimization of a class of relational expressions
ACM Transactions on Database Systems (TODS)
Equivalences Among Relational Expressions with the Union and Difference Operators
Journal of the ACM (JACM)
Conjunctive query containment revisited
Theoretical Computer Science - Special issue on the 6th International Conference on Database Theory—ICDT '97
Static analysis in datalog extensions
Journal of the ACM (JACM)
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Exploiting Uniqueness in Query Optimization
Proceedings of the Tenth International Conference on Data Engineering
Decidable Containment of Recursive Queries
ICDT '03 Proceedings of the 9th International Conference on Database Theory
Containment of Aggregate Queries
ICDT '03 Proceedings of the 9th International Conference on Database Theory
VLDB '87 Proceedings of the 13th International Conference on Very Large Data Bases
Improved Unnesting Algorithms for Join Aggregate SQL Queries
VLDB '92 Proceedings of the 18th International Conference on Very Large Data Bases
MiniCon: A scalable algorithm for answering queries using views
The VLDB Journal — The International Journal on Very Large Data Bases
Answering queries using views: A survey
The VLDB Journal — The International Journal on Very Large Data Bases
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
Equivalences among aggregate queries with negation
ACM Transactions on Computational Logic (TOCL)
Equivalence of queries combining set and bag-set semantics
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
The containment problem for Real conjunctive queries with inequalities
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Deciding equivalences among conjunctive aggregate queries
Journal of the ACM (JACM)
Bag equivalence of XPath queries
Proceedings of the 13th International Conference on Database Theory
Bag equivalence of tree patterns
ACM Transactions on Database Systems (TODS)
Equivalence and minimization of conjunctive queries under combined semantics
Proceedings of the 15th International Conference on Database Theory
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The query equivalence problem has been studied extensively for set-semantics and, more recently, for bag and bag-set semantics. However, SQL queries often combine set, bag and bag-set semantics. For example, an SQL query that returns a multiset of elements may call a subquery or view that returns a set of elements. Queries may access both relations that do not contain duplicates, as well as relations with duplicates. As another example, in SQL one can compute a multiset-union of queries, each of which returns a set of answers. This paper presents combined semantics, which formally models query evaluation combining set, bag and bag-set semantics. The equivalence problem for queries evaluated under combined semantics is studied. A sufficient condition for equivalence is presented. For several important common classes of queries necessary and sufficient conditions for equivalence are presented.