# Conjunctive Query

In database theory, a conjunctive query is a restricted form of first-order queries. A large part of queries issued on relational databases can be written as conjunctive queries, and large parts of other first-order queries can be written as conjunctive queries. Conjunctive queries also have a number of desirable theoretical properties that larger classes of queries (e.g., the relational algebra queries) do not share.

### Other articles related to "conjunctive query, query, conjunctive":

Boolean Conjunctive Query
... In the theory of relational databases, a Boolean conjunctive query is a conjunctive query without distinguished predicates, i.e ... a query in the form, where each is a relation symbol and each is a tuple of variables and constants the number of elements in is equal to the arity of ... Such a query evaluates to either true or false depending on whether the relations in the database contains the appropriate tuples of values ...
Conjunctive Query - Formal Properties of Conjunctive Queries
... Conjunctive queries are one of the great success stories of database theory in that many interesting problems that are computationally hard or undecidable for ... For example, consider the query containment problem ... Given a query and a relational database instance, we write the result relation of evaluating the query on the instance simply as ...
Complexity Of Constraint Satisfaction - Equivalence Conditions - Conjunctive Query Evaluation and Containment
... Since the homomorphism problem is equivalent to conjunctive query evaluation and conjunctive query containment, these two problems are equivalent to ...

### Famous quotes containing the word query:

Such condition of suspended judgment indeed, in its more genial development and under felicitous culture, is but the expectation, the receptivity, of the faithful scholar, determined not to foreclose what is still a question—the “philosophic temper,” in short, for which a survival of query will be still the salt of truth, even in the most absolutely ascertained knowledge.
Walter Pater (1839–1894)