我想問下數據庫功能??

In computing, a database can be defined as a structured collection of records or data that is stored in a computer so that a program can consult it to answer queries. The records retrieved in answer to queries become information that can be used to make decisions. The computer program used to manage and query a database is known as a database management system (DBMS). The properties and design of database systems are included in the study of information science.

The term "database" originated within the computing discipline. Although its meaning has been broadened by popular use, even to include non-electronic databases, this article is about computer databases. Database-like records have been in existence since well before the Industrial Revolution in the form of ledgers, sales receipts and other business-related collections of data.

The central concept of a database is that of a collection of records, or pieces of information. Typically, for a given database, there is a structural description of the type of facts held in that database: this description is known as a schema. The schema describes the objects that are represented in the database, and the relationships among them. There are a number of different ways of organizing a schema, that is, of modeling the database structure: these are known as database models (or data models). The model in most common use today is the relational model, which in layman's terms represents all information in the form of multiple related tables each consisting of rows and columns (the true definition uses mathematical terminology). This model represents relationships by the use of values common to more than one table. Other models such as the hierarchical model and the network model use a more explicit representation of relationships.

Database management systems are usually categorized according to the data model that they support: relational, object-relational, network, and so on. The data model will tend to determine the query languages that are available to access the database. A great deal of the internal engineering of a DBMS, however, is independent of the data model, and is concerned with managing factors such as performance, concurrency, integrity, and recovery from hardware failures. In these areas there are large differences between products.

Eng. details please click:
http://en.wikipedia.org/wiki/Database

数据库（港、台地区称为资料库），可以被视为能够进行自动查询和修改的数据集。数据库有很多种类型，从最简单的存储有各种数据的表格到能够进行海量数据存储的大型数据库系统都在各个方面得到了广泛的应用。

数据库模型
数据库存在多种模型。而应用于大型数据储存的数据库一般为网状数据库（Network Database）、关系数据库（Relational Database）以及物件導向式資料庫（Oracle 即擁有此特性）。此外也有應用在LDAP（轻量级数据访问协议）的階層式資料庫（Hierarchical Database）。

表格数据库一般在形式上是一个二维陣列。一般来讲，数组中每列表示一个数据类型。数据在其中以不同行的形式存储。表格数据库模型是电子試算表（比如Excel）的基础。


[数据库的索引
資料索引的觀念由來已久，像是一本書前面幾頁都有目錄，目錄也算是索引的一種，只是它的分類較廣，例如車牌、身份証字號、條碼等，都是一個索引的號碼，當我們看到號碼時，可以從號碼中看出其中的端倪，若是要找的人、車或物品，也只要提供相關的號碼，即可迅速查到正確的人事物。

另外，索引跟欄位有著相應的關係，索引即是由欄位而來，其中欄位有所謂的關鍵欄位(Key Field)，該欄位具有唯一性，即其值不可重複，且不可為"null"。例如：在合併資料時，索引便是扮演欲附加欄位資料之指向性用途的角色。故此索引為不可重複性且不可為空。


資料庫的優缺點
資料庫的優點:

減少資料重複(Reduced Redundancy)
整合資料(Integrated data)
完整性(Integrity)
資料的共通性
可保護資料的安全及隱私

資料庫的缺點:

整體作業成本會增加
使用上較複雜
需經常備份,否則意外狀況將造成重大傷害
資料庫管理師(DBA)不容易培訓
多套系統，格式有所出入，後續整合管理不易

chinese details please click:
http://zh.wikipedia.org/wiki/%E6%95%B0%E6%8D%AE%E5%BA%93

Microsoft Access
數據庫﹝UIT﹞

Microsoft Access 是一套效果極佳及功能強大的專業資料庫處理軟件，不但能管理極大量的資料及處理極繁複的查詢及合併多個大型或小型的資料庫。除了資料管理及查詢分析外，Access亦能提供自定的資料輸入表格、圖表製作及統計報告表等。