Tuesday, January 6, 2015

Database Query Languages

Database Query Languages / What is database query language? / List of popular query languages / Query languages for Database systems or Information Retrieval systems

Database Query Languages

Database query languages are languages or interfaces that are used to write queries into databases or information systems. These can be broadly categorized into two major categories Database Query Languages or Information Retrieval Query Languages.

Ideally, a query language allows users to formulate their queries in a simple and intuitive way, without having any special proficiency in the technicalities of the database besides knowledge of the (relevant part of the) database schema.

In this post, I have listed some of the widely used database query languages;

  • SQL – Most widely used query language for relational databases is Structured Query Language (SQL). SQL was one of the first commercial languages for Edgar F. Codd's relational model, as described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks."[10] Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database language.

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  • OQL – Object Query Language (OQL) is a type of query language standard created after SQL for handling Object-oriented Databases. Originally developed by Object Data Management Group (ODMG), OQL supports the model named ODMG. It deals with complex objects without privileging the set construct and the select-from-where clause.

To read more - OQL book , OQL for O2 database

  • XQUERY – It is a type of query language used for accessing XML data sources. XQuery is designed to query XML data - not just XML files, but anything that can appear as XML, including databases. It is designed by W3C (World Wide Web Consortium), standards organization for the World Wide Web.

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  • Datalog – It is the query language for handling Deductive Databases. Datalog is a declarative logic language in which each formula is a function-free Horn clause, and every variable in the head of a clause must appear in the body of the clause.

  • CQL – Contextual Query Language (CQL) is a formal language for representing queries to information retrieval systems such as web indexes or bibliographic catalogues and museum collection information. The design objective is that queries be human readable and writable, and that the language be intuitive while maintaining the expressiveness of more complex languages. CQL tries to combine simplicity and intuitiveness of expression for simple, every day queries, with the richness of more expressive languages to accommodate complex concepts when necessary.

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  • SPARQL – It is an RDF query language, that is, a semantic query language for databases, able to retrieve and manipulate data stored in Resource Description Framework format. SPARQL is developed by W3C.

To read more - SPARQL home page

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