JavaServer Pages, 3rd Edition

Table Example

If you develop a database-driven web application from scratch, you must first develop a database schema. The database schema shows how the persistent information in the application is modeled as a set of related tables. For a large application, this is a great deal of work, and it’s extremely important to find the right balance between flexibility and performance of frequent queries. How database schemas are developed is beyond the scope of this book, but there are plenty of other books available on this subject. Examples are C.J. Date’s classic and very academic An Introduction to Database Systems (Addison Wesley), and a book that’s easier to read, Database Design for Mere Mortals: A Hands-On Guide to Relational Database Design by Michael J. Hernandez (Addison Wesley). In the event that you’re developing a web interface to an existing database, the schema development is already taken care of, but you still need to study the schema to make sure you understand how all the tables fit together.

The schema for the example in this chapter is simple. To store the employee information, we need only the table described in Table 12-1.

Table 12-1. Employee database table

Column name	SQL data type	Primary key?
UserName	CHAR (Text)	Yes
Password	CHAR (Text)	No
FirstName	CHAR (Text)	No
LastName	CHAR (Text)	No
Dept	CHAR (Text)	No
EmpDate	DATE (Date/Time)	No
EmailAddr	CHAR (Text)	No
ModDate	TIMESTAMP (Date/Time)	No

In a relational database, one column (or ...