A Relational Database can be expressed in terms of tables and the schemas for these tables. A database can contain several tables and their schemas, which define the structure of tables. Each table has a primary key that is used to uniquely define every record (row) in the table. Foreign keys are used to define the relations between different tables in a database.
The goal for an RDBMS (Relational Database Management System) is to maintain the data (in tables) and to quickly locate the requested data. Data can be requested through Query Languages.
Another important goal for an RDBMS is query optimization, which deals with finding the best possible method for evaluating the given queries. The optimization in this case is in terms of time taken for evaluation and the reliability of the query responses.
Databases part of Data Mining provide the fast and reliable access to data.