Broadly, query languages can be classified according to whether they are database query languages or information retrieval query languages. Examples include:

• .QL is a proprietary object-oriented query language for querying relational databases;
• Common Query Language (CQL) a formal language for representing queries to information retrieval systems such as as web indexes or bibliographic catalogues.
• CODASYL;
• D is a query language for truly relational database management systems (TRDBMS);
• DMX is a query language for Data Mining models;
• Datalog is a query language for deductive databases;
• ERROL is a query language over the Entity-relationship model (ERM), especially tailored for relational databases;
• Gellish English is a language that can be used for queries in Gellish English Databases , for dialogues (requests and responses) as well as for information modeling and knowledge modeling;
• ISBL is a query language for PRTV, one of the earliest relational database management systems;
• LDAP is an application protocol for querying and modifying directory services running over TCP/IP.
• MQL is a cheminformatics query language for a substructure search allowing beside nominal properties also numerical properties;
• MDX is a query language for OLAP databases;
• OQL is Object Query Language;
• OCL (Object Constraint Language). Despite it's name, OCL is also an object query language and a OMG standard.
• OPath, intended for use in querying WinFS Stores;
• Poliqarp Query Language is a special query language designed to analyze annotated text. Used in the Poliqarp search engine;
• QUEL is a relational database access language, similar in most ways to SQL;
• SMARTS is the cheminformatics standard for a substructure search;
• SPARQL is a query language for RDF graphs;
• SQL is a well known query language for relational databases;
• SuprTool is a proprietary query language for SuprTool, a database access program used for accessing data in Image/SQL (TurboIMAGE) and Oracle databases;
• TMQL Topic Map Query Language is a query language for Topic Maps;
• XQuery is a query language for XML data sources;