# relational calculus

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Related to relational calculus: Tuple relational calculus

## relational calculus

(database)
An operational methodolgy, founded on predicate calculus, dealing with descripitive expressions that are equivalent to the operations of relational algebra. Codd's reduction algorithm can convert from relational calculus to relational algebra.

Two forms of the relational calculus exist: the tuple calculus and the domain calculus.

["An Introduction To Database Systems" (6th ed), C. J. Date, Addison Wesley].

## relational calculus

The rules for combining and manipulating relations; for example De Morgan's law, "the complement of a union is equal to the union of the complements."
References in periodicals archive ?
This section introduces the systematic procedure to translate tuple relational calculus expressions to SQL queries.
The main idea in SQLNF is to eliminate universal quantifiers from the relational calculus expression.
Recall the normalized relational calculus expression of Query 1:
The complete query and its corresponding relational calculus expression is given next.
These corollaries give, among other things, an elementary proof that parity can not be defined using relational calculus with polynomial inequality constraints.
As in the case of relational calculus and algebra, we often consider queries that do not extend the active domain.
Relational calculus is just first-order logic over the database schema: its expressions are of the form e = {x|[Psi](x)} where [Psi](x) is a FO formula in the language of the schema relations.
Section 6 shows that the computational complexity in testing relational calculus with gap-order or set order, or stratified Datalog with gap-order or set order programs is safe in PTIME.
If [Phi] is a relational calculus formula and x is a variable, then [exists]x([Phi]) is a relational calculus formula.
Each relational calculus formula is evaluable as either true or false with respect to the input database and an assignment to the free variables.
Logicality, then, defined for Tarski the broadest notion of what constitutes a relational calculus.
finding, object models, pruning, relational calculus, relational specifications, symmetry

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