Accessing a database

An application server lets you work with server side resources such as 

databases. For example, a dynamic page may instruct the application server 

to extract data from a database and insert it into the page's HTML. For 

more information, see 

Appendix A,  Beginner's Guide to Databases 

 in 

Using Dreamweaver.

The instruction to extract data from a database is called a database query. A 

query consists of search criteria expressed in a database language called 

SQL (Structured Query Language). The SQL query is written into the 

page's server side scripts or tags. 

An application server cannot communicate directly with a database because 

the database's proprietary format renders the data undecipherable in much 

the same way that a Microsoft Word document opened in Notepad or 

BBEdit may be undecipherable. The application server can communicate 

with the database only through the intermediary of a database driver: 

software that acts like an interpreter between the application server and the 

database. 

After the driver establishes communication, the query is executed against 

the database and a recordset is created. A recordset is a set of data extracted 

from one or more tables in a database. The recordset is returned to the 

application server, which uses the data to complete the page.

Here's a simple database query written in SQL:

SELECT lastname, firstname, fitpoints

FROM employees

This statement creates a three column recordset and fills it with rows 

containing the last name, first name, and fitness points of all employees in 

the database. For more information, see 

Appendix B,  SQL Primer 

 in 

Using Dreamweaver. 

222 Understanding Web Applications