RELATIONAL
DATABASE MANAGEMENT
A relational database management system (RDBMS) is a
program that lets you create, update, and administer a relational database.
Most commercial RDBMS's use the Structured Query Language (SQL) to access the
database, although SQL was invented after the development of the relational
model and is not necessary for its use.
The leading RDBMS products are Oracle,
IBM's DB2 and Microsoft's SQL Server. Despite repeated challenges by competing
technologies, as well as the claim by some experts that no current RDBMS has
fully implemented relational principles, the majority of new corporate
databases are still being created and managed with an RDBMS.
RDBs organize data
in different ways. Each table is known as a relation, which contains one or
more data category columns. Each table record (or row) contains a unique data
instance defined for a corresponding column category.
One or more data or
record characteristics relate to one or many records to form functional
dependencies. These are classified as follows:
·
One to One: One table record relates to
another record in another table.
·
One to Many: One table record relates to
many records in another table.
·
Many to One: More than one table record
relates to another table record.
·
Many to Many: More than one table record
relates to more than one record in another table.
RDB performs "select", "project"
and "join" database operations, where select is used for data
retrieval, project identifies data attributes, and join combines relations.
RDBs have many other advantages, including:
·
Easy extendability, as new data may be
added without modifying existing records. This is also known as scalability.
·
New technology performance, power and
flexibility with multiple data requirement capabilities.
·
Data security, which is critical when
data sharing is based on privacy. For example, management may share certain
data privileges and access and block employees from other data, such as
confidential salary or benefit information.