Editing Database (section)

==Database languages==

Database languages are special-purpose languages, which allow one or more of the following tasks, sometimes distinguished as [[sublanguage]]s:

* [[Data control language]] (DCL) – controls access to data;
* [[Data definition language]] (DDL) – defines data types such as creating, altering, or dropping tables and the relationships among them;
* [[Data manipulation language]] (DML) – performs tasks such as inserting, updating, or deleting data occurrences;
* [[Data query language]] (DQL) – allows searching for information and computing derived information.

Database languages are specific to a particular data model. Notable examples include:

* SQL combines the roles of data definition, data manipulation, and query in a single language. It was one of the first commercial languages for the relational model, although it departs in some respects from [[Codd's 12 rules|the relational model as described by Codd]] (for example, the rows and columns of a table can be ordered). SQL became a standard of the [[American National Standards Institute]] (ANSI) in 1986, and of the [[International Organization for Standardization]] (ISO) in 1987. The standards have been regularly enhanced since and are supported (with varying degrees of conformance) by all mainstream commercial relational DBMSs.{{sfn|Chapple|2005}}<ref name="IBM-sql">{{cite web | title = Structured Query Language (SQL) | publisher = International Business Machines | url = http://publib.boulder.ibm.com/infocenter/db2luw/v9/index.jsp?topic=com.ibm.db2.udb.admin.doc/doc/c0004100.htm | date = October 27, 2006 | access-date = 2007-06-10 }}</ref>
* [[Object Query Language|OQL]] is an object model language standard (from the [[Object Data Management Group]]). It has influenced the design of some of the newer query languages like [[JDOQL]] and [[EJB QL]].
* [[XQuery]] is a standard XML query language implemented by XML database systems such as [[MarkLogic]] and [[eXist]], by relational databases with XML capability such as Oracle and Db2, and also by in-memory XML processors such as [[Saxon XSLT|Saxon]].
* [[SQL/XML]] combines [[XQuery]] with SQL.{{sfn|Wagner|2010}}

A database language may also incorporate features like:

* DBMS-specific configuration and storage engine management
* Computations to modify query results, like counting, summing, averaging, sorting, grouping, and cross-referencing
* Constraint enforcement (e.g. in an automotive database, only allowing one engine type per car)
* Application programming interface version of the query language, for programmer convenience