The defining characteristic of a database is (arguably) the data model that it implements. A data model is an abstract, logical definition of the objects used to model the structure of data and the operators used to model its behavior.

The most popular type of DBMS - and the only type that is as widely used today are the relational database systems, based on the relational data model.

Relational systems dominate the DBMS marketplace. Briefly (and loosely), a relational system is one in which:

1. The data is perceived by the user as tables (and nothing but tables); and

2. The operators available to the user (e.g. for retrieval) are operators

that generate new tables from old.

The term relation is basically just a mathematical term for a table.

DB2 (IBM), Ingres (pr. ingress), Informix, SQL Server (Microsoft), Sybase, MySQL and PostgreSQL.

Advocates of the object-oriented approach extol their virtues most strongly for complex application areas, including science and medicine.

Also known as deductive, expert, or knowledge-based systems. As the names suggest, these are database systems based on logic or reasoning.

More often than not, database designers are concerned with designing, implementing and querying databases that use a relational model. Therefore, the relational database model is likely to be the most widely used database to date.

Some topics in this essay:
MySQL PostgreSQL, Object Oriented, Example Oracle, database systems, , IBM Ingres, object systems, relational systems, relational database, database model, data model, relational database model, model relational, relational system, systems based, database systems based, relational dbms,