A database (its abbreviation is BD, in English DB, database) is an entity in which it is possible to store data in a structured manner and with the least redundancy possible. These data must be usable by programs, by different users. Thus, the basic notion of data is usually coupled to a network in order to be able to put together this information, hence the name bank. There is generally talk of information system to designate the whole structure that gathers the organized means to share data.

Usefulness of a database?

A database makes it possible to make data available to users for a query, an introduction or an update, ensuring the rights assigned to the latter. This is even more useful when computer data is becoming more and more numerous.

A database can be local, that is, usable on a machine by a user, or distributed, meaning that the information is stored on remote machines and accessible by network.

The essential advantage of using databases is the possibility of being accessed by multiple users simultaneously.

The management of databases

In order to be able to control the data as well as the users, the need for a management system made itself felt quickly. The management of the database is made thanks to a system called SGBD (database management system) or DBMS (Database management system). The SGBDis a set of services (software applications) that allow managing databases, that is to say:

• allow easy access to data
• authorize access to information to multiple users
• manipulate the data present in the database (insertion, deletion, modification)

The SGBD can be broken down into three subsystems:

• the file management system: allows the storage of information on a physical medium
• internal DBMS: manages the issuance of information
• external DBMS: represents the user interface

To Data Manipulation Language (dml) is used to manipulate the contents of the database. The most commonly used dml is sql.

The term database should not be confused with Database Management System (DBMS). O sgbd is the system software used to create and manage databases and provide users and applications with access to database(s). A database is a DBMS as a document is a word processor .

Here are some of the many Dbms found in the market today:

• mysql
• postgresql
• oracle
• sqlite
• sqlserver
• Sybase

Some useful references:

• Design
• Manage a database
• Tuning of a database
• Database security
• Database connections
• Database normalization