The web and databases

keywords:
online ordering 在线订货
brower 浏览器
peer-to-peer 对等
retrieval 检索
E-commerce 电子商务
E-business 电子企业
script 脚本 稿本 过程
dynamic web page 动态web网页
static web page 静态web网页
hyperlink 超链接
form 表单，表格，窗体
database query 数据库查询
middleware 中间件
CGI 公用网关接口
API 应用程序接口
PHP 个人家庭主页
ASP 现在服务器页面，动态服务器主页

Databases are extremely common on the world wide web, Vitually all companies that offer products or corporate information, online ordering, or similar activities through a web site use a database, the most common applications involve client server database transactions, where the user’s brower is the client software, The use of peer to peer information exchange, however. is increasing.

1.examples of web databases in use.
There are scores of examples of how databases can be used on the web, databases facilitie information retrieval and processing, as well as allow more interactive, dynamic content, following these sections is a dicussion and example of how a web database might work and a brief look at other web database related issus.

1)Information retrival
By the very nature, databases lend themselves to information retrival on the web, which is, in essence, a hug storehouse of data waiting to be retrieved, Data is stored in the database, and web site visitors can request and view it.

2)E-commerce and E-business
Another widely used database application on the web is to support and facilitie e-commerce, catalog information, pricing, customer information, shopping cart contens, and more be stored in a database to be retrieved on demand using an appropriate script or program to link the database with the web site.

3)dynamic web pages
static web pages display the same information for everyone, every time the page is display, untill the web page file is modified, in contract, the appearance and content of dynamic web pages change based on a user’s input. This input can be based ib selections specified on a form located on the page or controlled by some othe aspect, sunch as a java applet. Active X control. or the activities that the user has already performed on the sites, sunch as clicking a displayed ad or a product’s hyperlink.

2.how web databases work
1)an example about database and the web work together
To further illustrate more about how databases and the web can work together, let’s look at an example.

The request to retrive information from or store data into a web database is usually initiated by the user, Filling out a web page form, selecting an opetion from a menu displayed on a web page, or clicking an onscreen are common ways database requests are made, The request is retrived by the web server, which then converts the request into a database query and passes it on to the database server with help of intermediary software called middleware. the database server retrives the appropriate information and returns it to the web server（again. via middleware） where it is displayed on the user’s screen as a web page, these steps are illustrated in fig 9-10

2)middleware
software that connects two otherwise separate applications sunch as web server and a database management system, as in fig 9-10 is referred to as middleware. the most common types of middleware used to interface between a database and a web page are CGI and API script, a newer scripting language becomong increasingly more popular is php and asp