Databases

A relational database presents data as a collection of tables.

A table consists of a defined set of columns and any number of rows. The data in each table is logically related, and relationships can be defined between tables. Data can be viewed and manipulated based on mathematical principles and operations called relations (such as, INSERT, SELECT, and UPDATE).

A database is self-describing in that it contains, in addition to data, a description of its own structure. It includes a set of system catalog tables, which describe the logical and physical structure of the data; a configuration file, which contains the parameter values associated with the database; and a recovery log, which records ongoing transactions and transactions that can be archived.

Databases can be local or remote. A local database is physically located on the workstation in use, while a database on another machine is considered remote.