On conjunctive queries containing inequalities
نویسندگان
چکیده
منابع مشابه
Bag Equivalence of Bounded Symmetry-Degree Conjunctive Queries with Inequalities
We consider the problem of checking equivalence of conjunctive queries with inequalities under bag (multiset) semantics. The problem is known to be decidable in pspace and as hard as graph isomorphism, but its exact complexity remains open. We introduce a natural restriction based on what we call the symmetry degree of queries, and show that when the symmetry degree is bounded by a fixed polyno...
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A query Q is said to be effectively bounded if for all datasets D, there exists a subset DQ of D such that Q(D) = Q(DQ), and the size of DQ and time for fetching DQ are independent of the size of D. The need for studying such queries is evident, since it allows us to compute Q(D) by accessing a bounded dataset DQ, regardless of how big D is. This paper investigates effectively bounded conjuncti...
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ژورنال
عنوان ژورنال: Journal of the ACM
سال: 1988
ISSN: 0004-5411,1557-735X
DOI: 10.1145/42267.42273