Data Manipulation Language (DML) is a language that enables users to access or manipulate data as organised by the appropriate data model. The types of access are :
1. Retrieval of information stored in the database
2. Insertion of information stored in the database
3. Deletion of information stored in the database
4. Modification of information stored in the database
There are basically two types of DML :
1. Procedural DMLs : It require a user to specify what data are needed and how to get those data.
2. Declarative DMLs : It is also known as non-procedural DML. It require a user to specify what data are needed without specifying how to get those data.
Query : A query is a statement requesting the retrieval of information. The portion of a DML that involves information retrieval is called a query language.
The levels of abstraction also apply at the manipulation of data. At the physical level, we must define algorithms that allow efficient access to data. At higher levels of abstraction, we emphasize ease of use.
The goal is to allow users to interact efficiently with the system. The query processor component of the database system translates DML queries into sequences of actions at the physical level of the database system.