Introduction to Databases
Contents
Getting Organized
What is a Database?
Database Structure
Forms and Layouts
Sorting
Queries
Building a Database
Summary
Getting Organized
Jose: Gathering all of this
data for our group project was a lot of work. How do we organize it?
Brian: Really. Piles of paper on the table are only going to
make the job harder! Who needs that?
Deena: I guess the way to begin is to set up a structure for this mess.
Heather: Let's take a look at constructing a database. I have
some information on databases.
What is a Database?
A database is like a filing cabinet. It can be a computer file but it
doesn't have to be. It is a flexible way to store organize,
reorganize, and report related information for distribution.
Database Structure
Sage: So, how does a database work? What are its parts?
Heather: Let's see...
A database file is a collection
of related information. Each file stores information about one
topic.
A database consists of one or more records of
information. Each record is a collection of information about one person,
place, or thing.
A record contains all the pieces of information about
a particular subject. For example, if you had a database of the people
with whom you correspond, each record would contain information on one
person. If your database contained twenty records, you would have
information on twenty people. |
 |
Each record in a database contains different pieces of information called fields .
A field is just one component
of the record and contains one item in the record.
In the example of a database of people with whom you correspond, each record
might have a name field, an address field, and a telephone number field.
Activity 1:
The following are examples of databases:
- telephone book
- national plant database (http://plants.usda.gov/)
- census data
- medical records
- various research databases
Using the "My Notes" tool on the right side of the tool bar at the
top of the page, think of some other examples of databases and describe some
of the ways that databases make storing and accessing information easier.
Database fields come in a variety of types.
Text (or character): A text field may contain any
character. In an electronic database, a numeric character designated as text
may NOT be used in calculations.
Numeric: A numeric field can ONLY contain a number
and may be used in calculations.
Date: A field classified as a date may be used in
day/date calculations. The user may choose different data formats to
suit specific information needs.
Boolean: Boolean fields are "logical" fields that
can have one of two values (e.g., true or false).
Other types of fields include picture fields (for graphics), calculation fields
(useful for mathematical manipulation of one or more fields in the same
record), and summary fields (useful for mathematical manipulation
of fields from different records).
Activity 2:
Check to see if you understand the parts of a database; complete this
quiz (ANGEL Quiz).
Activity 3:
Whether you think about it or not, many of your daily, weekly, and monthly
activities involve using databases. For example, if you have used the library
recently, you accessed a database. Take a few minutes to describe some possible
interactions you have had with computerized databases in the last month, using
the "My
Notes" tool
on the right side of the tool bar at the top of the page.
Forms and Layouts
Deena: OK. I understand about creating records
and fields, and you said that most electronic database programs have them. How
can I get the information into a special form? Say a mailing list
for printing labels?
Heather: Simple. You use forms or layouts.
Once the database structure (records and fields) is defined, most database
programs create a standard form or layout for entering the data.
Most databases are capable of displaying the data using different forms
or layouts. These forms or viewing layouts do not change the data, they
just change what you see. In the example of a database of people with
whom you correspond, you may have an entry form (for entering new data) and
a mailing label form (for printing mailing labels).
Another way to think about this is to consider a house as your data and
the windows as a way to view the data. As you move around outside
the house and peer in through different windows (layouts), you will see different
aspects of the house (data). Through one window you may see the living
room, through another the kitchen, and through another, the living room and
the kitchen. The house (data) doesn't change, just the way you look
at it.
Using a database, the user might: enter or import data, edit data,
browse data, query data, sort data, print reports, letters, labels, and
other output, or export data for other uses.
Sorting
Jose: If we enter all of the information correctly, what would be
the fastest way to find something without looking through each record individually?
Heather: We sort the data.
Sorting a database means arranging the records in a specific way to make reported
data more usable.
An alphabetic sort will arrange text data in ascending alphabetic order. If
specified, the text fields can also be sorted in descending order.
Queries
Brian: What if I want to find something in a big
electronic database? Do
I have to look at each record?
Heather: No, you can use queries to find what you want.
The data in a database is not useful unless it can be accessed and data
extracted in order to answer questions. The process of extracting
specific data from a database is called a query.
A query searches the database for specific data matching some criteria. A
query can have one criterion or may be made up of multiple criteria.
You can output resulting matches from a query in a variety of formats, including
labels, lists, and reports.
Activity 4:
Check to see if you understand sorting and searching; take
this quiz (ANGEL Quiz) .
Building a Database
Deena: OK. I think I understand the basics of how to use a database. What
if I want to make one myself?
Heather: The most important thing is to plan ahead and to have a
plan.
Since you have to define each of the fields that comprise the record, it
is important to have a clear idea about what information you're going to
store in the database.
Here is one possible model to follow if you design your own database:
- Identify the overall purpose of the database.
- Identify all data that is to be kept in the database.
- Identify appropriate hardware/software to meet the analysis requirements
of the database.
- Design the database to meet the criterion identified in steps 1 and 2.
- Implement the database on a small scale (30 records or less) and check
its performance.
- Revise as needed. Do steps 4-5 several times, if necessary.
- Implement the entire database.
As the data is entered it is important to be as accurate and consistent
as possible. Accuracy and consistency are very important for retrieval
of information.
For example, suppose you had a database that had a field about transportation. In
one record you entered, "car." In the other record you entered, "auto." When
you do a search on this database, looking for "car," only the first record
will appear.
So, in addition to being very careful about consistency with your database,
keep in mind that other databases you use my have this problem. That's
why you need to use several terms to search any database accurately. In
this example, you might want to search for "car" AND "auto" AND "automobile."
Tips:
- Don't use a capital O in place of a zero (0). Records with a capital
O will sort differently than records with a zero (0)
- Don't use an l (el) in place of a one (1). Records with an l (el) will
sort differently than records with a one (1).
Summary
Heather: I think we should review our database plans
so that when we add information we are consistent and complete. Does
everyone agree?
Everyone: Yes.
Heather: OK then, Sage and Jose, go for it!
Sage: OK. We all agree that the database will store information
in a planned format for future retrieval.
Jose: We will use sorts to present the data in different
ways.
Brian: We will need to structure our queries carefully in order to be able
to retrieve the information we need.
Deena: We can also develop forms and layouts to view different aspects
of the data.
Jose: We definitely need to plan ahead in designing the fields for
the database.
Brian: And make sure that we are accurate and consistent in the data
entry.
Heather: Sounds like you guys got the idea. Let's make our
database!
Activity 5:
Databases and Privacy
Often when people talk about computerized databases, the issue of how much
data about a person is collected and maintained by companies, the government,
universities, etc. is discussed. Take a few moments to think about what kinds
of privacy issues there are with the databases you delineated in the previous
activities and answer the following questions using the "My Notes" tool .
- How do you feel about the information being collected about you?
- Are these sources of information a threat to your privacy?
- In what ways could this data be abused?
Activity 6:
A Job Search Database
One of the reasons many students are involved in higher education is to
prepare themselves for a career or perhaps for a change in careers. Finding
a job with the “right” company in the location you want involves
a lot of preparation, searching, and learning how to interview. A database
of companies or organizations that interest you would be a useful project
to begin now, and continue to develop as you further your studies. This database,
along with your continuing reflection on your interests, abilities, experiences,
and values will help as you work toward career goals and decide about things
such as your major, part-time, or summer work, and elective courses.
Using a database program like Microsoft Access, build yourself a job search
database. Think about what kind of records you want to construct in
order to build and maintain a database about job possibilities. What fields
should be included in those records? Depending on how experienced you are
with computers and software, you could build your database using database
software (like Microsoft Access) or a spreadsheet.
If you aren't comfortable with computers, or you don't have access to
a database program, just build your database on index cards. Then, compare
your database with a classmate's or friend's.
- Are they similar?
- What kinds of records have you chosen?
- What have other students chosen?
- Make revisions to your database. It will be useful to you, especially
when you are working with career services personnel on your campus
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