Introduction to this concept and special features.
A database management system is defined as the set of programs that administer and manage the information contained in a database. It helps to perform the following actions:
- Data definition
- Maintaining data integrity within the database
- Data security and privacy control
- Data manipulation
A database management system is composed of:
The database manager
It is a set of programs that are not visible to the end user and are responsible for privacy, integrity, data security and interaction with the operating system. It provides an interface between the data, the programs that handle it, and the end users.
Any operation that the user does against the database is controlled by the manager.
The manager stores a description of data in what we call a data dictionary, as well as the allowed users and permissions.
There must be an administrator user in charge of centralizing all these tasks.
Data Dictionary
It is a database where all the properties of the database, description of the structure, relationships between the data, etc. are stored.
The dictionary must contain:
- The external, conceptual and internal description of the database
- data restrictions
- access to data
- User account descriptions
- User permissions
- The external schemes of each program
The database administrator
It is a person or group of people responsible for the control of the database management system.
The main tasks of an administrator are:
- The definition of the logical and physical schema of the database
- The definition of user views
- Assigning and editing permissions for users
- Maintenance and monitoring of security in the database
- General maintenance of the database management system
languages
A database management system must provide a series of languages for the definition and manipulation of the database. These languages are the following:
- Data Definition Language (DDL). To define database schemas
- Data Manipulation Language (DML). To manipulate data in the database
- Data Control Language (DCL). For user administration and security in the database.
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