Data storage and processing issues have been and still are in the centre of attention of computer science professionals and database users. Technologies (memory volumes, processor frequencies) have evolved rapidly. At the same time demands have raised even more rapidly. One of the main data processing technologies is using database. Initially it was created as an attempt to eliminate the main drawbacks of file management systems.
Different logical models of databases are used: hierarchical (tree), network, relational and object data models. The most common models are relational and object-relational data models. Relational and object algebras are the basis of these models.
Database server programming languages are used widely during the last years. These languages facilitate processing of large and complicated data volumes. Flexibility of the database is facilitated by the server programming languages, too, because it simplifies implementation of necessary changes.