Databases

Database (DB) - a collection of related data organized according to specific rules providing for the general principles of description, storage and manipulation, independent of the applications. The database is information model of subject field.

Accessing databases is carried out by using a database management system (DBMS). DBMS provides support for the creation of databases, centralized management and the organization of access to them of various users.

DBMSs are classified by the method of access to the database:

• File-server. In the file-server DBMS the data files are located centrally on the file server. DBMS is located on each client computer. Access of DBMS to the data is carried out via a local network. (For example, dBase).
• Client-server. Client-server DBMS is located on the server together with a database and provides access to the database in exclusive mode. All client requests for data processing  are processed by client-server DBMS centrally. (For example, Oracle, MS SQL Server, PostgreSQL, MySQL).

Scheme of work with a database:

Creation of the database alias.

Main concepts about database tables.

Creation of database table.

Change of database table structure.