外文翻譯----數(shù)據(jù)庫和數(shù)據(jù)倉庫

1、畢業(yè)設(shè)計(jì)（論文）外文翻譯1Database and Data WarehousesWhat is a Database?What is a database? A database is a collection of related data items. It is generally stored on secondary storage devices that allow rapid direct access to indi

2、vidual data items. Redundancy is minimized; where possible, only a single copy if a data item exists. The database may be used by many different application systems at once, eliminating the need for separate systems to m

3、aintain the data for each application .When a user program inquires if a particular item is in the database, a database management system (DBMS) does the actual searching. The user does not need to be familiar with the f

4、ormat in which the data is stored or the actual physical location of the data.The DBMS cerates the database, keeps it up-to-date, and provides reday access to authorized user. Database management systems also provide ext

5、ensive security measures to prevent unauthorized access. They make it convenient for expressing relationship between related data items and facilitate the design of user application systems. They provide backup and recov

6、ery capabilities to prevent against loss or destruction of vital information. They ensure database integrity, that is, what is supposed to be in the database is there and what is not supposed to be .isn’t. a person calle

7、d the database administrator determines who may access the database, modify it, add new relationships ,and the like. This is a very important lifeline. The real question in database management systems is how to organize

8、information to provide rapid answers to the kinds of questions users are likely to ask. The same data organized differently can yield drama-tidally different access speeds. There common ways are used to structure a datab

9、ase to indicate the relationships among the data items; these are the relational database, the hierarchical data-base, and the network database.Hierarchical, Network, and Relational Databases (three principal logical dat

10、abase models)The Hierarchical Model In a hierarchical database, data records are arranged in a strict parent child relationship. Each parent record may have many children, but each child record has exactly one parent. F

11、igure 3-1 shows a simple hierarchical database, indicating the relationship between a customer and the orders it has placed with a company. Searching a hierarchical database is rapid and convenient as long as it is searc

12、hed from the top down. IBM’s IMS (Information 畢業(yè)設(shè)計(jì)（論文）外文翻譯3AccountsAccount Balance Type173921 1700.00 Checking251101 888.00 Savings… … …Heading the columns are the three attributes: Account No, Balance, and Type. Below t

13、he attributes are the rows, or records. The first row says that account number 173921 has a balance of one thousand and seven hundreds dollars, and it is checking account .Suppose we wanted to know the balance of account

14、 173921.We could ask this Query in SQL as follows:SELECT balance FORM Accounts WHERE accountNo=173921IBM’s DB2 and Oracle from the Oracle Corporation are examples of mainframe relational database management systems. Micr

15、osoft Access is a PC relational database management system. (Oracle also has a PC version).Client-Server ArchitectureMany varieties of modern software use a client-server architecture, in which requests by one process (t

16、he client) are sent to another process (the server) for execution. Database systems are no exception. In the simplest client/server architecture, the entire DBMS is a server, except for the query interfaces than interact

17、 with user and send queries or other commands across to the server. For example, relational systems generally use the SQL language for representing requests from the client to the server. The database server then sends t

18、he answer, in the form of a table or relation, back to the client. The relationship between client and server can get more complex especially when answers are extremely large. There is also a trend to put more work in th

19、e client, since the server will be a Bottleneck if there are many simultaneous database users.New Forms of Database and Data WarehousesObject-Oriented Database Object-oriented databases store data as objects that can b

20、e automatically retrieved and shared. Included in the object are the processing instructions to complete each database transaction. These objects can contain various types of data, including sound, graphics, and video as