Java Programming with Oracle SQLJ

2.1. Relational Databases

A relational database is a collection of information that has been organized into tables. Each table contains rows with entries organized into columns. Tables are stored in distinct storage areas known as schemas. A schema may be thought of as an area in which an individual user of the database may store his or her tables—schemas serve to separate tables created by one user from those created by another.

What does the term relational mean when used in the context of a database? It indicates that there are relationships between the columns in the database tables. This is an important concept, and you will learn more about it later in this chapter. The relational database model for the representation of data was developed by Dr. E. F. Codd in the early 1970s, and was described in his paper titled "A Relational Model of Data for Large Shared Data Banks," published in Communications of the ACM (Association for Computing Machinery) Vol. 13, No. 6, June 1970.

We are all familiar with data represented in the form of tables. For example, customer information can be represented as a table of rows containing the customer's first name, last name, date of birth, and phone number:

first_name last_name  dob         phone
---------- ---------- ----------- ------------
John       Smith      01-JAN-1965 650-555-1212
Cynthia    Stevens    05-MAR-1968 650-555-1213
Steve      Seymour    16-JUN-1971 650-555-1214
Gail       Williams   01-DEC-1975 650-555-1215
Doreen     Heyson     20-AUG-1970 650-555-1216

The data in a ...