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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Data query language</span></span>
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</style><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="Query_language" title="Query language">Query language</a>.</div>
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<p><b>Data query language</b> (<b>DQL</b>) is part of the base grouping of <a href="SQL" title="SQL">SQL</a> sub-languages. These sub-languages are mainly categorized into four categories: a data query language (DQL), a <a href="Data_definition_language" title="Data definition language">data definition language</a> (DDL), a <a href="Data_control_language" title="Data control language">data control language</a> (DCL), and a <a href="Data_manipulation_language" title="Data manipulation language">data manipulation language</a> (DML). Sometimes a transaction control language (TCL) is argued to be part of the sub-language set as well.
</p><p>DQL statements are used for performing queries on the data within schema objects. The purpose of DQL commands is to get the schema relation based on the query passed to it.
</p><p>Although often considered part of DML, the SQL <a href="Select_(SQL)" title="Select (SQL)">SELECT</a> statement is strictly speaking an example of DQL. When adding FROM or WHERE data manipulators to the SELECT statement the statement is then considered part of the DML.
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<div class="mw-heading mw-heading2"><h2 id="Related_language_types">Related language types</h2></div>
<ul><li><a href="Data_definition_language" title="Data definition language">Data definition language</a></li>
<li><a href="Data_manipulation_language" title="Data manipulation language">Data manipulation language</a></li>
<li><a href="Data_control_language" title="Data control language">Data control language</a></li>
<li><a href="Transactional_control_language" class="mw-redirect" title="Transactional control language">Transactional control language</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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</style><div id="Database414" style="font-size:114%;margin:0 4em"><a href="Database" title="Database">Database</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Main</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database#Major_database_usage_requirements" title="Database">Requirements</a></li>
<li><a href="Database_theory" title="Database theory">Theory</a></li>
<li><a href="Database_object" title="Database object">Database object</a></li>
<li><a href="Database_model" title="Database model">Models</a></li>
<li><a href="Database_management_system" class="mw-redirect" title="Database management system">Database management system</a></li>
<li><a href="Database_machine" title="Database machine">Machine</a></li>
<li><a href="Database_engine" title="Database engine">Engine</a></li>
<li><a href="Database_server" title="Database server">Server</a></li>
<li><a href="Database_application" title="Database application">Application</a></li>
<li><a href="Database_connection" title="Database connection">Connection</a>
<ul><li><a href="Datasource" title="Datasource">datasource</a></li>
<li><a href="Data_Source_Name" class="mw-redirect" title="Data Source Name">DSN</a></li></ul></li>
<li><a href="Database_administrator" title="Database administrator">Administrator</a></li>
<li><a href="Synonym_(database)" title="Synonym (database)">Synonym</a></li>
<li><a href="Lock_(database)" class="mw-redirect" title="Lock (database)">Lock</a></li>
<li>Types</li>
<li><a href="Comparison_of_database_tools" class="mw-redirect" title="Comparison of database tools">Tools</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Database#Database_languages" title="Database">Languages</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Data_definition_language" title="Data definition language">Data definition</a></li>
<li><a href="Data_manipulation_language" title="Data manipulation language">Data manipulation</a></li>
<li><a href="Query_language" title="Query language">Query</a>
<ul><li><a href="Information_retrieval_query_language" class="mw-redirect" title="Information retrieval query language">information retrieval</a></li></ul></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Database_security" title="Database security">Security</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database_activity_monitoring" title="Database activity monitoring">Activity monitoring</a></li>
<li><a href="Database_audit" title="Database audit">Audit</a></li>
<li><a href="Database_forensics" title="Database forensics">Forensics</a></li>
<li><a href="Negative_database" title="Negative database">Negative database</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Database_design" title="Database design">Design</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Entity%E2%80%93relationship_model" title="Entity–relationship model">Entities and relationships</a> (and <a href="Enhanced_entity%E2%80%93relationship_model" title="Enhanced entity–relationship model">Enhanced</a> notation)</li>
<li><a href="Database_normalization" title="Database normalization">Normalization</a></li>
<li><a href="Database_schema" title="Database schema">Schema</a></li>
<li><a href="Database_refactoring" title="Database refactoring">Refactoring</a></li>
<li><a href="Cardinality_(data_modeling)" title="Cardinality (data modeling)">Cardinality</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Programming</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database_abstraction_layer" title="Database abstraction layer">Abstraction layer</a></li>
<li><a href="Object%E2%80%93relational_mapping" title="Object–relational mapping">Object–relational mapping</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Management</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database_virtualization" title="Database virtualization">Virtualization</a></li>
<li><a href="Database_tuning" title="Database tuning">Tuning</a>
<ul><li><a href="Database_caching" title="Database caching">caching</a></li></ul></li>
<li><a href="Data_migration#Database_migration" title="Data migration">Migration</a></li>
<li><a href="Database_preservation" title="Database preservation">Preservation</a></li>
<li><a href="Database_integrity" class="mw-redirect" title="Database integrity">Integrity</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Lists_of_databases" title="Lists of databases">Lists of</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="List_of_academic_databases_and_search_engines" title="List of academic databases and search engines">Academic</a></li>
<li><a href="List_of_biological_databases" title="List of biological databases">Biological</a></li>
<li><a href="List_of_biodiversity_databases" title="List of biodiversity databases">Biodiversity</a></li>
<li><a href="List_of_facial_expression_databases" title="List of facial expression databases">Facial expression</a></li>
<li><a href="List_of_online_databases" title="List of online databases">Online</a></li>
<li><a href="List_of_online_music_databases" title="List of online music databases">Online music</a></li>
<li><a href="List_of_online_real_estate_databases" title="List of online real estate databases">Online real estate</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">See also</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database-centric_architecture" title="Database-centric architecture">Database-centric architecture</a></li>
<li><a href="Intelligent_database" title="Intelligent database">Intelligent database</a></li>
<li><a href="Two-phase_locking" title="Two-phase locking">Two-phase locking</a></li>
<li><a href="Locks_with_ordered_sharing" title="Locks with ordered sharing">Locks with ordered sharing</a></li>
<li><a href="Load_file" title="Load file">Load file</a></li>
<li><a href="Database_publishing" title="Database publishing">Publishing</a></li>
<li><a href="Halloween_Problem" title="Halloween Problem">Halloween Problem</a></li>
<li><a href="Log_shipping" title="Log shipping">Log shipping</a></li></ul>
</div></td></tr><tr><td class="navbox-abovebelow hlist" colspan="2"><div><b><span class="noviewer" typeof="mw:File"><span title="WikiProject"></span></span> WikiProject</b> <b><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</b></div></td></tr></tbody></table></div>
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<ul><li><a href="Object_database" title="Object database">Object-oriented</a>
<ul><li><a href="Comparison_of_object_database_management_systems" title="Comparison of object database management systems">comparison</a></li></ul></li>
<li><a href="Relational_database" title="Relational database">Relational</a>
<ul><li><a href="List_of_relational_database_management_systems" title="List of relational database management systems">list</a></li>
<li><a href="Comparison_of_relational_database_management_systems" title="Comparison of relational database management systems">comparison</a></li></ul></li>
<li><a href="Key%E2%80%93value_database" title="Key–value database">Key–value</a></li>
<li><a href="Column-oriented_DBMS" class="mw-redirect" title="Column-oriented DBMS">Column-oriented</a>
<ul><li><a href="List_of_column-oriented_DBMSes" title="List of column-oriented DBMSes">list</a></li></ul></li>
<li><a href="Document-oriented_database" title="Document-oriented database">Document-oriented</a></li>
<li><a href="Wide-column_store" title="Wide-column store">Wide-column store</a></li>
<li><a href="Graph_database" title="Graph database">Graph</a></li>
<li><a href="NoSQL" title="NoSQL">NoSQL</a></li>
<li><a href="NewSQL" title="NewSQL">NewSQL</a></li>
<li><a href="In-memory_database" title="In-memory database">In-memory</a>
<ul><li><a href="List_of_in-memory_databases" title="List of in-memory databases">list</a></li></ul></li>
<li><a href="Multi-model_database" title="Multi-model database">Multi-model</a>
<ul><li><a href="Comparison_of_multi-model_databases" title="Comparison of multi-model databases">comparison</a></li></ul></li>
<li><a href="Cloud_database" title="Cloud database">Cloud</a></li>
<li><a href="Blockchain-based_database" title="Blockchain-based database">Blockchain-based database</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Concepts</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database" title="Database">Database</a></li>
<li><a href="ACID" title="ACID">ACID</a></li>
<li><a href="Armstrong's_axioms" title="Armstrong's axioms">Armstrong's axioms</a></li>
<li><a href="Codd's_12_rules" title="Codd's 12 rules">Codd's 12 rules</a></li>
<li><a href="CAP_theorem" title="CAP theorem">CAP theorem</a></li>
<li><a href="Create%2C_read%2C_update_and_delete" title="Create, read, update and delete">CRUD</a></li>
<li><a href="Null_(SQL)" title="Null (SQL)">Null</a></li>
<li><a href="Candidate_key" title="Candidate key">Candidate key</a></li>
<li><a href="Foreign_key" title="Foreign key">Foreign key</a></li>
<li><a href="PACELC_design_principle" title="PACELC design principle">PACELC design principle</a></li>
<li><a href="Superkey" title="Superkey">Superkey</a></li>
<li><a href="Surrogate_key" title="Surrogate key">Surrogate key</a></li>
<li><a href="Unique_key" title="Unique key">Unique key</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Objects</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Relation_(database)" title="Relation (database)">Relation</a>
<ul><li><a href="Table_(database)" title="Table (database)">table</a></li>
<li><a href="Column_(database)" title="Column (database)">column</a></li>
<li><a href="Row_(database)" title="Row (database)">row</a></li></ul></li>
<li><a href="View_(SQL)" title="View (SQL)">View</a></li>
<li><a href="Database_transaction" title="Database transaction">Transaction</a></li>
<li><a href="Transaction_log" title="Transaction log">Transaction log</a></li>
<li><a href="Database_trigger" title="Database trigger">Trigger</a></li>
<li><a href="Database_index" title="Database index">Index</a></li>
<li><a href="Stored_procedure" title="Stored procedure">Stored procedure</a></li>
<li><a href="Cursor_(databases)" title="Cursor (databases)">Cursor</a></li>
<li><a href="Partition_(database)" title="Partition (database)">Partition</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Components</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Concurrency_control" title="Concurrency control">Concurrency control</a></li>
<li><a href="Data_dictionary" title="Data dictionary">Data dictionary</a></li>
<li><a href="Java_Database_Connectivity" title="Java Database Connectivity">JDBC</a></li>
<li><a href="XQuery_API_for_Java" title="XQuery API for Java">XQJ</a></li>
<li><a href="Open_Database_Connectivity" title="Open Database Connectivity">ODBC</a></li>
<li><a href="Query_language" title="Query language">Query language</a></li>
<li><a href="Query_optimization" title="Query optimization">Query optimizer</a></li>
<li><a href="Query_Rewriting" class="mw-redirect" title="Query Rewriting">Query rewriting system</a></li>
<li><a href="Query_plan" title="Query plan">Query plan</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Functions</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database_administration" title="Database administration">Administration</a></li>
<li><a href="Query_optimization" title="Query optimization">Query optimization</a></li>
<li><a href="Replication_(computing)#DATABASE" title="Replication (computing)">Replication</a></li>
<li><a href="Shard_(database_architecture)" title="Shard (database architecture)">Sharding</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related topics</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Database_model" title="Database model">Database models</a></li>
<li><a href="Database_normalization" title="Database normalization">Database normalization</a></li>
<li>Database storage</li>
<li><a href="Distributed_database" title="Distributed database">Distributed database</a></li>
<li><a href="Federated_database_system" title="Federated database system">Federated database system</a></li>
<li><a href="Referential_integrity" title="Referential integrity">Referential integrity</a></li>
<li><a href="Relational_algebra" title="Relational algebra">Relational algebra</a></li>
<li><a href="Relational_calculus" title="Relational calculus">Relational calculus</a></li>
<li><a href="Relational_model" title="Relational model">Relational model</a></li>
<li><a href="Object%E2%80%93relational_database" title="Object–relational database">Object–relational database</a></li>
<li><a href="Transaction_processing" title="Transaction processing">Transaction processing</a></li></ul>
</div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div>
<ul><li><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</li>
<li><span class="noviewer" typeof="mw:File"><span title="Outline"></span></span> <a href="Outline_of_databases" title="Outline of databases">Outline</a></li></ul>
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