computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includin ...

, domain relational calculus (DRC) is a calculus that was introduced by Michel Lacroix and

Alain Pirotte Alain may refer to: People * Alain (given name), common given name, including list of persons and fictional characters with the name * Alain (surname) * "Alain", a pseudonym for cartoonist Daniel Brustlein * Alain, a standard author abbreviation u ...

as a declarative database query language for the

relational data model The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of ...

.Michel Lacroix, Alain Pirotte
Domain-Oriented Relational Languages
VLDB 1977: 370-378 In DRC, ''queries'' have the form: :

\

where each X_i is either a domain variable or constant, and

p(\langle X_1, X_2, ...., X_n \rangle)

denotes a DRC ''formula''. The result of the query is the set of tuples X₁ to X_n that make the DRC formula true. This language uses the same operators as tuple calculus, the logical connectives ∧ (and), ∨ (or) and ¬ (not). The existential quantifier (∃) and the universal quantifier (∀) can be used to bind the variables. Its computational expressiveness is equivalent to that of relational algebra. E. F. Codd
Relational Completeness of Data Base Sub-languages
In R. Rustin, editor, Data Base Systems. Prentice Hall, 1972

Examples

Let (A, B, C) mean (Rank, Name, ID) in the Enterprise relation and let (D, E, F) mean (Name, DeptName, ID) in the Department relation All captains of the starship USS Enterprise:

\left\

In this example, A, B, C denotes both the result set and a set in the table Enterprise. Names of Enterprise crew members who are in Stellar Cartography:

\begin
\ \\
\end

In this example, we're only looking for the name, and that's B. The condition F = C is a requirement that describes the intersection of Enterprise crew members AND members of the Stellar Cartography Department. An alternate representation of the previous example would be:

\left\

In this example, the value of the requested F domain is directly placed in the formula and the C domain variable is re-used in the query for the existence of a department, since it already holds a crew member's ID.

References

{{reflist

External links

DES – An educational tool for working with Domain Relational Calculus and other formal languages

WinRDBI – An educational tool for working with Domain Relational Calculus and other formal languages
Relational model Logical calculi

Examples

See also

References

External links