Learning Oracle PL/SQL

3.1. Some Background on the Example

The programming examples in this book center around building a system that will assist in the cataloging and searching of library books—a kind of "cardless" electronic catalog. In my hypothetical library, all the library's operational data is to reside in an Oracle database. How will the actual catalog information—title, author, and the like—get stored in Oracle? One way is for librarians to enter the data by hand. In later chapters, you will see a way the data can be loaded automatically from a remote source, and how library patrons search and retrieve information once it's in the catalog.

For now, I'd like to address two requirements:

• Allow the creation of catalog entries for each newly acquired book

• Provide a means of counting how many copies of a particular book the library owns

Implementing the first requirement demonstrates a PL/SQL procedure that inserts data into the database. The program for the second requirement will show you a PL/SQL function in action. Before you can understand how to write either of these programs, you'll need an understanding of the design of the underlying database.

3.1.1. The Data Model

As with many projects undertaken by PL/SQL developers, the database has already been designed and built for us, presumably based on the best knowledge of user requirements that was available. The database subset relevant to the two requirements at hand contains information about each copy of each book in the library. Figure ...