Chapter 2: Database Fundamentals

This chapter discusses fundamental concepts such as relational databases, SQL, and database access programming interfaces.

Relational Databases

Almost all enterprise applications use a database to store and retrieve data belonging to the business domain. These databases are often managed by a relational database management system (RDBMS) and less often by an object database management system. Whichever database management system (DBMS) is used, its role in the corporate information system is predominant. The DBMS offers a lot of features other than a centralized view of what may be a distributed database architecture. DBMSs ensure availability, integrity, consistency, concurrency, security of the corporate data through access control, and a lot more. Such DBMS facilities lighten all client programs because they aren’t involved in these issues.

The Java Database Connectivity (JDBC) interface allows Java applets, servlets, and applications to access data in popular database management systems. The standard for accessing data is SQL, which permits maximum interoperability; SQL is the language used with JDBC. JDBC is a software layer that enables developers to write real client/server projects in Java. JDBC doesn’t concern itself with specific DBMS functions.

Relational databases are the most common DBMSs. A main characteristic of a relational database is the absolute separation between physical and logical data. Data is accessed through the associated logical model to avoid supplying physical storage locations and to reduce the limitations imposed by using physical information. Relational databases enable the definition of relations and integrity rules between data sets. E.F. Codd developed this model at the IBM San Jose Research Lab in the 1970s. SQL, a language to handle, define, and control data, was also developed at the IBM lab. SQL stands for Structured Query Language; it is a query language that interacts with a DBMS. It enables data access without supplying physical access plans, data retrieval as sets of records, and performing complex computations on the data.