Sagiv Y. Quadratic algorithms for minimizing join in restricted relational expressions. SIAM Journal of Computing 12, 2 (May 1983), 316--328.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....28] Some researchers used additional information to rewrite queries. The most obvious candidates for use are integrity constraints (ICs) 35, 36] arbitrary predicates over the database that must hold for any instance (e.g. a primary key) In this context, ICs have been used to rewrite queries [24, 25, 30, 33, 34, 37]. For example, Paulley and Larson [24, 25] rewrite to eliminate unnecessary group by and distinct operations; Sun and Yu [37] rewrite to eliminate unnecessary joins, add beneficial restrictions, and eliminate redundant non beneficial restrictions. Functional dependencies (FDs) are a primary type ....

Sagiv Y. Quadratic algorithms for minimizing join in restricted relational expressions. SIAM Journal of Computing 12, 2 (May 1983), 316--328.

....queries without actually searching the databases. Moreover, as will be shown, solving the IRC refuting problem enables us to solve, in the context of semantically constrained database instances, the following problems: query containment problem for conjunctive queries ( 4] 1] 2] 33] [32], 16] 17] 20] 37] 38] 9] 18] 40] redundant join problem; redundant selection condition problem, and redundant implication constraint problem ( 5] 35] 39] etc. Note that referential constraints essentially express the inclusion dependencies (INDs) and implication ....

Y. Sagiv, "Quadratic algorithms for minimizing joins in restricted relational expressions" SIAM J.comput. 12,2(May 1983), pp316--329.

....one for equality queries. We also give interesting examples to show that queries outside these classes do not have the property. 1 Introduction The containment and minimization problems of equality queries (conjunctive queries with no inequalities) have been investigated intensively in the past ([1, 2, 3, 6, 7, 8, 13, 14, 15]) In [3] it is shown that a query Q 1 contains a query Q if and only if there is a homomorphism from Q 1 to Q; and the minimization can be achieved by using foldings, which are self homomorphisms; and both problems are NP complete. The problems for (in)equality queries (conjunctive queries ....

Sagiv,Y. Quadratic algorithms for minimizing joins in restricted relational expressions. SIAM J.comput. 12,2(May 1983), pp316-329.

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