Domain relational calculus

In computer science, domain relational calculus (DRC) is a calculus that was introduced by Michel Lacroix and Alain Pirotte as a declarative database query language for the relational data model.^{[1]}
In DRC, queries have the form:
where each X_{i} is either a domain variable or constant, and denotes a DRC formula. The result of the query is the set of tuples X_{i} to X_{n} which makes 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.^{[2]}
Examples
Let (A, B, C) mean (Rank, Name, ID)
and (D, E, F) to mean (Name, DeptName, ID)
Find all captains of the starship USS Enterprise:
In this example, A, B, C denotes both the result set and a set in the table Enterprise.
Find Names of Enterprise crewmembers who are in Stellar Cartography:
In this example, we're only looking for the name, and that's B. F = C is a requirement, because we need to find Enterprise crew members AND they are in the Stellar Cartography Department.
An alternate representation of the previous example would be:
In this example, the value of the requested F domain is directly placed in the formula and the C domain variable is reused in the query for the existence of a department, since it already holds a crew member's id.
See also
 Relational algebra
 Relational calculus
 Aldat Relational Algebra
 Domain algebra
References
Categories: Databases
 Data modeling
 Logical calculi
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