Database Management System

Dialogue

摘要：[对话训练]

Dialogue 1

A:Hey ,Greg , Check out my new wallpaper!

I scanned a bunch of pictures from our trip to Hawaii last summer.

B:I like it .But it must take up a lot of memory.

A: It's not too bad , Besides I've got a 20 Gig hard drive.so I've got plenty of room

Dialogue 2

A:Something is wrong with my computer screen.

Everything looks yellow.

B:Try wiggling the cable that attaches it to your computer.

A: Hey , it worked!

B: Sometimes that happens when the cable gets old and the connection isn't as good.

Dialogue 3

A:I keep getting so much spam in my e-mail.

What can I do about it?

B: If your account has filters, you can block certain senders,or re-route mail with certain content to a different folder.

A:I think my account does have filters, I'll have to check that out.

Dialogue 4

A: You're going to be gone for 3 weeks?

B:That's right.

A:You'll have a lot of e-mail to catch up with when you get back.

B:Actually, I'll have all my mail forwarded to a web-based account while I'm gone.

That way, I can keep up with it anywhere I can get on the Internet.

Professional Terms

passage

摘要：文章训练

Vocabularies

administrator n.

afford vt.

appropriate a.

cabinet n.

comprehensive a.

corporate a.

cross-referenced a.

extract vt.

folder n.

item n.

order v.

participate v.

payment n.

picture vt.

relevant a.

request n.

sort vt.

specialist n.

unpaid a.

Passages

A database is a large group of stored, integrated ( cross-referenced )data.

usually organized in files that can be retrieved and manipulated to produce information.

A database management system(DBMS) is a comprehensive software tool that allows users to create.

maintain ,and manipulate the database to produce the relevant management information.

By integrated we mean that the file records are logically related to one another so that all data on a topic can be retrieved by simple requests

The database management systems software represents the interface between the user and the computer's operating system and database.

Picture a typical corporate office with a desk , chairs ,telephone and a row of file cabinents along the wall.

A wide variety of business data is stored in these cabinets.

If the files have been carefully organized and maintained then any piece of data that needs to be retrieved can quickly be located and removed.

However ,if the data has not been properly filed, some time and effort will be expended to find it.

And ,regardless of how carefully the files have been organized and maintained, you will always need to retrieve related pieces of data.

For example ,suppose you need to review the customer files for all invoices for payments due in excess of $2,500 and prepare a simple report.

Notes

摘要：文章训练

How would you accomplish this task?

First ,you would probably go through the customer files in alphabetical order, foler by folder.

You would examine each invoice in the folders to determine if the amount is in excess of $2,500 and remove and copy each invoice that meets the criterion.

You would then have to refill the copies you removed and risk misfiling them

When you had examined all the customer folders and copied all the appropriate invoices.

you would then review the copies and put together your report.

Imagine how much time this would take.

If there are a lot of customers, you would need to spend hours if not days.

Now let's look at the situation in a different way.

The environment is the same , except that ,instead of file cabinets.

you have a microcomputer or a terminal and DBMS software that has access to a customer database file as shown in the following .

In this file a row of customer data is referred to as a record, and an individual piece of data within a record ,such as a name ,is referred to as a field.

To get the invoice data you need, you would do something like this.

Turn on the computer and the printer.

start up the DBMS software

Give the command to open up the customer database file stored on your disk ,which is similar in concept to manually opening up the customer file in a filing cabinet.

Give the command to search all the records in the database file and display copies of the records that meet your criterion.

that is the names of people with unpaid invoices greater than $2,500.

If you were using dBASE IV , a popular microcomputer DBMS ,the command would look something like.

If you were using SQL( Structured Query Language) the command would look like this.

In response to this command ,all the records in the file that have an invoice amount greater than $2,500 will be listed on the screen.

The SQL command would also sort the listing into order by name.

This whole procedure would take perhaps only five minutes or less.

DBMS

摘要：文章训练

The DBMS is a software tool designed to manage a large number of integrated ,share electronic file cabinets.

You describe the type of data you wish to store.

and the DBMS is responsible for creating the database file(s).

and providing an easy to use mechanism for storing ,retrieving and manipulating the data.

In small businesses, databases may be both created and operated by the user.

In moderate to large size business with extensive computer systems.

the corporate database is usually created by technical information speciallists, such as the database administrator.

but the database management system is acquired by the information systems department.

Users generate and extract data stored by the database management system.

As with systems analysis and design.

to design a database the organization must describe its informational needs to the designers and specify the type of data needed,

Users participate heavily in this process of defining what information needs to be stored in the database.

Since the early 1980s, tremendous advances have been made in developing database management systems for microcomputers.

They are now easy enough for users to learn to operate without assistance and powerful enough to produce valuable management information.

Regardless of whether you're in a large or a small business ,you cannot afford to do without the capabilities that a DBMS can provide.

Notes

Regardless of whether you're in a larger or a small business ,you cannot afford to do without the capabilities that a DBMS can provide.