Database language

As a database language is called formal languages ​​that have been developed for use in database systems. With the help of the database language communicates a user or a program with the database, or the DBMS. As an important part of the work with database systems is the formulation of queries that is part of the language scope is usually the (database ) query language. Database languages ​​are tailored to the requirements in this environment ( database creation, maintenance and retrieval ) tailored. It can be described as a Turing - complete, but it is not about programming languages ​​in today's common sense - there can be no application software is written in order.

There are a number of database languages ​​, often tailored for specific DBMS. A standardized language for the widely used relational database systems ( RDBMS) is SQL, which is the superset of many proprietary implemented SQL dialects simultaneously. SQL itself does not prescribe how the commands are implemented, but only how the database behaves to the outside of certain operations.

Partitioning of relational database languages

A common categorization of the elements of relational database languages ​​are the three divisions DML, DDL and DCL.

  • Data Manipulation Language (DML German "computer language" ): language or language parts for the query, insert, modify, or delete user data
  • Data Definition Language (DDL German " data description language " ): language or language components for creating, modifying, and deleting data structures
  • Data Control Language (DCL, German " Data Inspectorate language" ): language or language parts for access control

Appears occasionally also a separate category Data Query Language ( DQL ) to query data in the literature. However, this classification is not universally accepted ( see the specific position of the query). Another special case is that of language elements to work with transactions inconsistently either the DML, DCL, or a separate category Transaction Control Language (TCL ) are assigned.

In SQL, all the items in a language are combined by different instructions. When historical database system IMS for DML and DDL there was own languages ​​( DL / I and assembler macros) that DCL has been implemented using the operating system.

Subdivision non-relational database languages

Unlike in the relational database model (physical data Description DSDL, ), a data description language (DDL logical data description) and data manipulation language ( DML) is in the network database model between a Data Storage Description Language distinction. This tripartite division is based on the more general ANSI - SPARC architecture was proposed as a standard by the Data Base Task Group, but could not prevail against the currently prevailing relational database model itself.

In still older hierarchical database model no subdivision was standardized in Part languages.

Query language versus database language

The terms query language and database language is sometimes mistakenly used interchangeably.

  • A database language goes beyond generally beyond the mere queries.
  • Query languages ​​are also in areas outside of database systems used.
ANSI-SPARC Architecture
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