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In 1970 the Communications of the ACM, a respected computer science journal, published a paper entitled "A Relational Model of Data for Large Shared Data Banks." Authored by Dr. E. F. Codd, a member of the IBM San Jose Research Laboratory, the paper provided a theoretical and mathematical foundation for the concept of a relational database. It is difficult to point to another single article in the field of computer science that has had as great an influence on vendors, practitioners, and users as Codd's contribution.
A relational database is an information system that presents information as rows contained in a collection of tables, each table possessing a set of one or more columns.
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In his paper, Codd described the elements of a relational database: relations, attributes, domains, and the relational operators. Codd's paper described a data storage system that possessed three characteristics that were sorely needed at that time:
It's important to understand the limitations of database systems that existed at that time. The average user—unless he or she were a programmer—could not retrieve data satisfying certain criteria unless a program were written to meet those needs. To simply increase the width of an existing field, such as zipcode, from five to nine characters, maintenance programmers would have to modify countless programs just to adjust field offsets. Many of these programs might not even contain a direct reference to zipcode, but the effect of increasing the width of a field rippled through these older database systems.
Some time passed before a commercial product actually implemented some of the features of the relational database that Codd described. During the early 1980s, the relational database became the foundation for decision support systems. The power of the relational database made it possible for business users to analyze data through interactive queries and reports without the need for programmers. In the late 1980s, continuing advancements in both hardware and relational technology increased the acceptance of the relational database in transaction processing systems.
| NOTE |
Today's relational databases implement a number of extremely useful features that Codd did not mention in his original article. However, as of this writing, no commercially available database fully implements Codd's rules for relational databases. |
Today, the relational database is at the core of the information systems for many organizations, both public and private, both large and small. Today many vendors sell relational
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database management systems (RDBMS); some of the more well-known vendors are Oracle, Sybase, IBM, Informix, Microsoft, and Computer Associates. Of these vendors, Oracle has emerged as the leader. The Oracle RDBMS engine has been ported to more platforms than any other database product. Because of Oracle's multiplatform support, many application software vendors have made Oracle their database platform of choice.
RDBMS (Relational Database Management System) is the software provided by a vendor such as Oracle Corporation that manages a relational database. An RDBMS supports the use of declarative statements which describe the rules that the data must satisfy. This feature is referred to as declarative integrity. An RDBMS is the principal component in a client/server architecture, which is discussed later in this lesson.
Structured Query Language (SQL) is a non-procedural language; unlike C or COBOL, in which you must describe exactly how to access and manipulate data, SQL specifies what to do. Internally, Oracle determines how to perform the request. SQL exists as an American National Standards Institute (ANSI) and International Standards Organization (ISO) standard as well as an industry standard. Oracle's implementation of SQL adheres to Level 2 of the ANSI X3.135-1989/ISO 9075-1989 standard with full implementation of the Integrity Enhancement Feature. As with other database vendors, Oracle provides many extensions to ANSI SQL.
Structured Query Language (SQL) is the official and de facto standard language for interfacing with a relational database.
In addition, Oracle's implementation of SQL adheres to the U.S. government standard as described in the Federal Information Processing Standard Publication (FIPS PUB) 127, entitled Database Language SQL.
As the world's leading vendor of relational database software, Oracle Corporation supports its flagship product, the Oracle RDBMS, on more than 90 platforms. The Oracle RDBMS is available in the following three configurations:
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The Oracle Universal Server includes several optional components:
The Oracle Workgroup Server is designed to serve a smaller group of users than the Oracle Universal Server. For example, a typical Oracle Workgroup Server installation might consist of a high-end Pentium server running Microsoft NT and supporting up to 25 users. The Workgroup Server automatically configures itself so that database administration tasks are minimized.
Personal Oracle provides almost all of the same features that the Oracle8 Server provides on larger platforms. As a result, you can use Personal Oracle to build a working database application that you can later port to a multiuser version of the Oracle8 Server. You can use Personal Oracle to build all the tables, indexes, views, sequences, and other database objects that would exist in a production-quality database application. At the present time, Personal Oracle is available on three platforms—Windows 3.11, Windows 95, and Windows NT.