Relational Model

A relational database is composed of many tables in which data are stored, but a relational database involves more that just the use of tables. Tables in a relational database must have unique rows, and the cells (the intersection of a row and column — equivalent to a field) must be single-valued (that is, each call must contain only one item of information, such as a name, address, or identification number). A relation database management system (RDBSM) allows data to be readily created, maintained, manipulated, and retrieved from a relational database.

In a relational database, data relationships do not have to be predefined. Users query a relational database and establish data relationships spontaneously by joining common fields. A database query language acts as an interface between users and a relational database management system. The language helps the users of a relational database to easily manipulate, analyse, and create reports from the data contained in the database.

Two basic query styles are used in a relational database: query by example, and structured query language. In query by example, the database management system displays field information and users enter inquiry conditions in the desired fields.