enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. Tuple relational calculus - Wikipedia

    en.wikipedia.org/wiki/Tuple_relational_calculus

    Since the calculus is a query language for relational databases we first have to define a relational database. The basic relational building block is the domain (somewhat similar, but not equal to, a data type). A tuple is a finite sequence of attributes, which are ordered pairs of domains and values. A relation is a set of (compatible) tuples ...

  3. Relation (database) - Wikipedia

    en.wikipedia.org/wiki/Relation_(database)

    A relational database consists of named relation variables (relvars) for the purposes of updating the database in response to changes in the real world. An update to a single relvar causes the body of the relation assigned to that variable to be replaced by a different set of tuples.

  4. Relational calculus - Wikipedia

    en.wikipedia.org/wiki/Relational_calculus

    The relational calculus is similar to the relational algebra, which is also part of the relational model: While the relational calculus is meant as a declarative language that prescribes no execution order on the subexpressions of a relational calculus expression, the relational algebra is meant as an imperative language: the sub-expressions of ...

  5. Relational model - Wikipedia

    en.wikipedia.org/wiki/Relational_model

    The body is a set of tuples. A tuple is a collection of n values, where n is the relation's degree, and each value in the tuple corresponds to a unique attribute. [6] The number of tuples in this set is the relation's cardinality. [7]: 17–22 Relations are represented by relational variables or relvars, which can be reassigned.

  6. QUEL query languages - Wikipedia

    en.wikipedia.org/wiki/QUEL_query_languages

    QUEL is a relational database query language, based on tuple relational calculus, with some similarities to SQL.It was created as a part of the Ingres DBMS effort at University of California, Berkeley, based on Codd's earlier suggested but not implemented Data Sub-Language ALPHA.

  7. Codd's theorem - Wikipedia

    en.wikipedia.org/wiki/Codd's_theorem

    Codd's theorem states that relational algebra and the domain-independent relational calculus queries, two well-known foundational query languages for the relational model, are precisely equivalent in expressive power. That is, a database query can be formulated in one language if and only if it can be expressed in the other.

  8. Domain relational calculus - Wikipedia

    en.wikipedia.org/wiki/Domain_relational_calculus

    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]

  9. Category:Relational model - Wikipedia

    en.wikipedia.org/wiki/Category:Relational_model

    Query by Example; R. Recursive join; Relation (database) Relational algebra; Relational calculus; Relational data mining; ... Tuple relational calculus; W. Weak entity