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relational database
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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
The first commercial RDBMS was the Multics Relational DataStore, first sold in 1978.
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.].