A DBMS is a software package that carries out many different tasks including the provision of facilities to enable the user to access and modify information in the database. The database is an intermediate link between the physical database, computer and the operating system and the users. To provide the various facilities to different types of users, a DBMS normally provides one or more specialized programming languages called database languages.
Database languages come in different forms. They are: -
1. Data Description Language (DDL)
2. Data Manipulation Language (DML)
Data Description Language (DDL)
As the name suggests, this language is used to define the various types of data in the database and their relationship with each other.
The basic functions performed by DDL are: -
• Create tables, files, databases and data dictionaries.
• Specify the storage structure of each table on disk.
• Integrity constraints on various tables.
• Security and authorization information of each table.
• Specify the structure of each table.
• Overall design of the Database.
Data Manipulation Language (DML)
A language that enables users to access or manipulate data (retrieve, insert, update, delete) as organized by a certain Data Model is called the Data Manipulation Language (DML). It can be of two types: -
1. Procedural DML - It describes what data is needed and how to get it. For example: - Relational Algebra.
2. Non Procedural DML - It describes what data is needed without specifying how to get it. For example: - Relational calculus.