Transcript Chapter 12

Chapter 12
Accessing Databases
Getting Started
• In this Chapter, you will learn:
− What’s a database
− About database software
− How to create your own database
− To create databases with spreadsheet software
− About databases on the Web and on CDs
− About Hardware: CDs and DVDs
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What’s a database?
• A database is a collection of data
• Structured databases contain information that is organized as
fields, records, and files
– A field contains a single piece of information
– A record contains fields of information about a single “entity” in the
database
– A group of similarly structured records form a fie
• A relational database allows you to store information for two
or more different types of records and form a link between
them
– Each record type is stored in a table
• For example, a video store database may include a table of customers and
a table of videos
• When a customer checks out a video a link is made between the two tables
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What’s a database?
Database with linked tables
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Do I need database software?
• Database software provides a set of tools to enter
and update information in fields
– Also called a database management system
– You can enter, delete, sort, and search for records
– You might access a product database when shopping
online or a bank database at an ATM machine
• Database software offers a wealth of data
management capabilities
– Requires a substantial learning commitment
– For simple files, you may be able to use the database
modules in Microsoft Works
– You can also use spreadsheet software for simple
databases
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How would I create my own database?
• Creating a database consists of two tasks:
– Creating the file structure to hold the data
– Entering the data
• A file structure is a specification for the database fields and
their characteristics
– You’ll need to assign a name to each field
– You may also need to specify the data type and maximum field length
• You then enter the data carefully and consistently
– Be consistent with symbols, capitalization, categories, and
abbreviations
– Compare onscreen data against the original documents
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How would I create my own database?
Entering data in Access
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Can I really create databases with
spreadsheet software?
• You can use spreadsheet software to maintain files of
information
• You cannot use it to join files or tables together to
create a relational database
• You can use the Form View feature in spreadsheet
software to view each row as a “card” containing a
series of fields
• You can also filter the data, which is more
complicated, but useful for creating reports that
show only selected data
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What about databases on the
Web and on CDs?
• You’ll find many databases on the Web
– Look up your old roommate in a phone-book-style
database
– Look up flights in a database of flight schedules
– Check the value of your car in a digital “Blue Book”
• Web and CD databases can overlap
– Web is optimal for data that is constantly changing
– On the Web databases can actively collect information
– CDs provide a low cost distribution method for less
changeable data
– CDs are more private since your access of the data is not
tracked by a cookie or a Web site
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What about databases on the
Web and on CDs?
Web and CD databases
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Hardware: CDs and DVDs
• CDs
− Originally invented to hold music
− CD-ROM
• Computer CDs are sometimes called CD-ROMs to distinguish
them from audio CDs
• CD-ROM is an abbreviation of “compact disc read-only memory”
• CD-ROMs are preloaded with data and cannot be used to store
additional data
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Hardware: CDs and DVDs
• CDs (continued)
− CD-R and CD-RW
• CD-R (CD-recordable) data cannot be changed once it is recorded
• CD-RW (CD-rewritable) allows you to record and then later
change the data
• CD-Rs are considered to be more dependable since some
machines have trouble reading CD-RWs created on other
machines
• Most CD drives have R and RW capabilities, and the speeds of
the drives vary
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Hardware: CDs and DVDs
CD Drive Speed Varies
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Hardware: CDs and DVDs
• DVDs
− Originally invented to replace VHS tapes
− Digital Video Disc
• Storage capacity much greater than a CD-ROM disc
• Data can be stored in one of four formats depending on number
of sides and number of layers used
• DVDs are available in read-only, recordable, and rewritable
formats
• High Definition DVD is a high-capacity DVD format designed for
high definition videos and data storage
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Hardware: CDs and DVDs
DVD storage capacity depends on sides
and layers used
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Hardware: CDs and DVDs
• Blu-ray disk is a competing format to High
Definition DVDs
• DVD drives often work with more than one
type of optical media
− DVD+R/RW / CD-R/RW combination drive can
read and record on both DVDs and CDs
− Most new PCs include a combination drive
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Who owns information about
me?
• What do you think?
– Can you identify an actual incident when you
discovered that data about you had been
distributed without your approval?
– Do you accurately fill out questionnaires that you
encounter on the Web?
– Do you think that you have the right to be
consulted before anyone distributes information
about you?
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Chapter Summary
• You should now be able to:
− Understand what is a database
− Use database software
− Create your own database
− Create databases with spreadsheet software
− Understand about databases on the Web and
on CDs
− Understand the difference CDs and DVDs
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