Different types of database languages and their features
Data Definition Language - Data definition language is a standard in command languages that defines different database structures. The statements in the language can be used for creating, removing or modifying database objects such as tables, indexes and users. The typical well known statements of the language are ALTER and CREATE. The concept of the language was originally launched in the Codasyl dbase model.
The database scheme was developed in a language describing fields, sets and records in the user data model. The model was gradually used to refer to a class of Structured Query Language for creating tables. Data definition language is also used to refer to a language for describing data structures.
Data Manipulation Language - Data manipulation language comprises of a class of language with commands designed for manipulation of data. The different manipulation steps in the language could be inserting data into tables, modification, retrieval or deletion of data. It is mostly used in the case of SQL databases. The language basically comprises of SQL data change statements. It could be used solely for the modification of the stored data, without affecting the database objects and schema.
Data Query Language - Data query language is designed to help extract data from databases. It is designed solely for the purpose of extracting data and doesn’t allow any type of data modification. The only command used in this type of language is SELECT. These languages are classified according to their application of database query or retrieving information. These two classes are different in that the first types provide factual answers to queries while the second types help find documents carrying information relevant to the query.
.QL is a type of data query language. It is an object oriented query language designed for querying relational dbases. Datalog is the later version of .QL. Contextual query language is another type of data query language. It is used for queries associated with systems designed for information retrieval such as web indexes and bibliographic catalogs. This query language is developed for dbases of the Codasyl type.