Query language

A query language ( Syn. : Query language , query language , search language , query language , filter language ) fachsprachlich after the English phrase Data Query Language also with the acronym DQL called, is a database language to search for information .

The result of a query ( query ) is a subset of the underlying information assets. One speaks therefore of filtering the data.

Query languages ​​are differentiated according to the purpose of their use or the degree of difficulty in using them. There are those for inexperienced or experienced users and for retrieval experts as well as system- related query languages ​​and system languages.

Query languages ​​can be translated into one another. So z. B. a query language for inexperienced users in a system-related intermediate language and this in turn translated into the system language.

Query languages ​​can be classified according to their cardinality . A query language A is more powerful than a query language B if A separates the database more clearly than B ; if the set of search result sets that can be formed in A includes the set of search result sets that can be formed in B.

Examples of query languages ​​in information systems

• A query language for XML information systems is the XML query language XQuery .
• The database language SQL contains a query language for database systems .
• The query function Query by Example contains a user-friendly field mask for simple queries.

See also

• Search engine (formulation of search queries)
• Phonetic search
• Information retrieval
• Relational algebra
• Range query

Wiktionary: query language  - explanations of meanings, word origins, synonyms, translations

literature

• Salton, Gerard and Michael McGill: Introduction to modern Information Retrieval. McGraw-Hill, 1983.
• Willenborg, Josef: Inquiry languages ​​for Internet information systems. Berlin, Humboldt-Univ., Diss., 2001. See here (PDF; 3.0 MB)