外文翻譯----數(shù)據(jù)庫(kù)和數(shù)據(jù)倉(cāng)庫(kù)(完整版)
【正文】 rts. The Relational Model In the early 1970s the relational database approach was developed to provide a much more userfriendly organization. Instead of using plex structures of pointers the relational database stores information simply as tables called relations. These tables are sometimes called flat because the rows of the table really are very much the same as the records of a file. Each row in a relation is called a record. Each column corresponds to a particular field within the record (fields are also called domains).The fields are headed by attributes, which describe the entries in the column. A relational database consists of one or more relations. A relational DBMS performs three primary operations on relations to form new relations: (1) Two relations may be joined (bined). (2) A relational may be projected (some of the columns are extracted form the relations and used to form the columns of the new relation). (3) Records may be selected according to various user specified criteria’s(Structured Query Language) is the most important query language based on the relational model. For instance, a relation named Accounts, record bank accounts, their balance, and type might look like: 畢業(yè)設(shè)計(jì)（論文）外文翻譯 3 Accounts Account Balance Type 173921 Checking 251101 Savings … … … Heading the columns are the three attributes: Account No, Balance, and Type. Below the 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 could ask this Query in SQL as follows: SELECT balance FORM Accounts WHERE accountNo=173921 IBM’s DB2 and Oracle from the Oracle Corporation are examples of mainframe relational database management systems. Microsoft Access is a PC relational database management system. (Oracle also has a PC version). ClientServer Architecture Many varieties of modern software use a clientserver architecture, in which requests by one process (the 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 with user and send queries or other mands 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 the answer, in the form of a table or relation, back to the client. The relationship between client and server can get more plex especially when answers are extremely large. There is also a trend to put more work in the client, since the server will be a Bottleneck if there are many simultaneous database users. New Forms of Database and Data Warehouses ObjectOriented Database Objectoriented databases store data as objects that can be automatically retrieved and shared. Included in the object are the processing instructions to plete each database transaction. These objects can contain various types of data, including sound, graphics, and video as well as traditional data and processing procedures. The objects can be shared and reused. These features of 畢業(yè)設(shè)計(jì)（論文）外文翻譯 4 Objectoriented databases promises to facilitate software development through reuse and the ability to build new multimedia application that bine multiple types of data. Benefit of Odom’s is their ability to support application for the World Wide Web, as described in the focus on Techn
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