relational database
     n : a database in which relations between information items are
         explicitly specified as accessible attributes; "in a
         relational database the data are organized as a number of
         differently sized tables"

	

	relational database
     
         (RDBMS - relational database management system) A
        database based on the relational model developed by
        E.F. Codd.  A relational database allows the definition of
        data structures, storage and retrieval operations and
        integrity constraints.  In such a database the data and
        relations between them are organised in tables.  A table is
        a collection of rows or records and each row in a table
        contains the same fields.  Certain fields may be designated
        as keys, which means that searches for specific values of
        that field will use indexing to speed them up.
     
        Where fields in two different tables take values from the same
        set, a join operation can be performed to select related
        records in the two tables by matching values in those fields.
        Often, but not always, the fields will have the same name in
        both tables.  For example, an "orders" table might contain
        (customer_id, product_code) pairs and a "products" table might
        contain (product_code, price) pairs so to calculate a given
        customer's bill you would sum the prices of all products
        ordered by that customer by joining on the product-code fields
        of the two tables.  This can be extended to joining multiple
        tables on multiple fields.  Because these relationships are
        only specified at retreival time, relational databases are
        classed as dynamic database management system.
     
        The first commercial RDBMS was the Multics Relational Data
        Store, first sold in 1978.
     
        INGRES, Oracle, Sybase, Inc., Microsoft Access, and
        Microsoft SQL Server are well-known database products and
        companies.  Others include PostgreSQL, SQL/DS, and RDB.
     
        ["Managing Data Bases, Four Critical Factors" Michael
        M. Gorman, QED Information Sciences, Inc.].
     
        ["An Introduction To Database Systems" (6th ed) C. J. Date,
        Addison Wesley (an excellent source of detailed info)].
     
        ["An End-User's Guide to Data Base" James Martin, Prentice
        Hall (excellent place to begin learning about DBMS)].
     
        (2002-06-10)