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1 Chapter
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2 Notes
Key Words and Expressions
table ['teibl] n. 表格 vt. 制表
column ['kɔləm] n. 列, 专栏, 纵队
row [rəu] n. 行 v. 划船
attribute [ə'tribju(:)t] n. 属性; 特性, 特质
record ['rekɔ:d] n. 记录 vi. 录音 a. 创记录的
manipulation [mənipju'leiʃən] n. 操纵, 控制
definition [defi'niʃən] n. 定义
gear [giə] vt. 使适应, 使适合, 调整
perform [pə'fɔ:m] vt. 执行; 完成; 做
identify [ai'dentifai] vt. 确认; 识别
uniquely [ju(:)‘ni:kli] ad. 独特地, 唯一地
constraint [kən'streint] n. 约束; 限制
primary key ['praiməriki:] 主键
foreign key ['fɔrinki:] 外键
scalability[skeilə‘biliti] n. 规模可伸缩性, 可升级
Database Basics
The database is now such an integral part of our day-to-day life that often we are not aware we are using one.
Our entire world is based on information. The telephone book, the schedule of a sports team, and a university’s timetable are all different types of databases. They take information and organize it in such a way that we can extract any information that we desire and act upon that information. Some databases are simple, such as a phone list; other databases are so large and complex, they need computer space greater than 100 PC’s combined. Databases can simplify our work and our lives by keeping us organized.
Databases are designed to offer an organized mechanism for storing,managing and retrieving information (检索信息). [1] They do so through the use oftables. If you’re familiar with spreadsheets (电子数据表) like Microsoft Excel, you’re probablyalready accustomed to storing data in tabular form (表格形式). It’s not much of a stretch to make theleap from spreadsheets to databases.
Tables
Just like Excel tables, database tables consist of columns (列) and rows (行). Each column contains a different typeof attribute (属性)and each row corresponds to a single record (记录).
For example, imagine that we werebuilding a database table that contained names and telephone numbers. We’dprobably set up columns named “ID”, “FirstName”, “LastName” and “Telephone”, then we’d simply startadding rows underneath those columns that contained the data we’re planning tostore, if we have 50 employees, we’d wind up with a table that contains 50rows.
Database
A Database include some tables, and you’re able to manipulate (操作) data: Retrieve all records that matchcertain criteria, Update records in bulk, Cross-reference records in differenttables, Perform complex aggregate calculations.
DBMS (Database Management System, 数据库管理系统)
A software system that enables users to define, create, maintain, andcontrol access to the database. The DBMS is the software that interacts withthe users’ application programs and the database. Figure 3-2 also shows.
Database Keys
= Key
A database key is an attribute utilized to sort and/or identify (确定) data in some manner. Each table has aprimary key (主键)which uniquely (唯一地)identifies records. Foreign keys (外键) are utilized to cross-reference databetween relational tables.
= Primary Keys
Every database table should have one or more colummsdesignated as the primary key. The value this key holds should be unique foreach record in the database. For example, we’d need to select an appropriateprimary key that would uniquely identify each employee.
Once you decide upon a primary key and set it up in the database, thedatabase management system will enforce the uniqueness of the key.[2] If youtry to insert a record into a table with a primary key that duplicates anexisting record, the insert will fail.
= Foreign Keys
The foreign keys are used to create relationships between tables.Natural relationships exist between tables in most database structures.
In Figure 3-4 shows the DepartmentID column in the Employees table is aforeign key that references the Departments table.
2. Database Software Options
Desktop Databases and ServerDatabases
Database Management Systems can be divided into two categories—desktopdatabases and server databases(as shown in Figure 3-5). Desktop databases areoriented toward single-user applications and reside on standard personalcomputers.
Desktop databases offer an inexpensive (便宜), simple solution to many less complexdata storage and manipulation requirements. Top 5 Desktop Databases are:Microsoft Access 2007, FilemakerPro, Alpha Five(Figure 3-6), Paradox and Lotus Approach.
Server databases contain mechanisms toensure the reliability (可靠性)and consistency (一致性)of data and are geared toward multi-user applications. [3] These databases aredesigned to run on high-performance servers and carry a correspondingly higherprice tag (标价).
Server databases, such as Microsoft SQL Server, Oracle and IBM DB2,offer organizations the ability to manage large amounts of data efficiently andin a manner that enables many users to access and update the datasimultaneously (同时地).If you’re able to carry the hefty price tag (负担得起的标价), a server-based database can provideyou with a comprehensive data management solution (全面的数据管理解决方案).
= Flexibility. Server-based databases canhandle just about any data management problem you can throw at them.
= Powerful performance. Server-baseddatabases are as powerful as you want them to be.
= Scalability (规模可伸缩性). Server databases are able togracefully handle a rapidly expanding amount of users and/or data.
Define Your Requirements
It’s important to do a careful needs analysis before you dive in andcommit to a database solution. You’ll often find that a desktop database issuitable for your business requirements when you originally planned to purchasean expensive server-based solution.[4]
