Information Technology Reference
In-Depth Information
A
record
is information about one instance of the data being stored,
such as one employee, one inventory item, or one sales transaction. Each
record contains one or more individual pieces of information, called a
field
. For example, in an Employees table, one of the fields might be
Badge Number, and another might be Hire Date. The software used
to create and control a database is a
database management system
(DBMS)
. For small, simple databases, many people use Microsoft
Access. For large-scale databases, a company might use an enterprise-
level database system like Oracle.
record
A row in a table, storing information about
a specific person, place, or thing.
field
A column in a table, storing one particular
kind of information, such as Phone or Name.
database management system (DBMS)
An application that helps users create and
manage databases.
A database program makes calculations and extrapolates information
using combinations of data and varying instruction sets. You might use it
to see how one item or person compares to another. For example, your
school uses a database to keep track of how well you're doing in com-
parison to your classmates across different subjects. Extracting informa-
tion from a database is known as
data mining
. Web searches make use
of data mining to provide search results based on the search query the
user enters.
data mining
Extracting information from a
database to zero in on certain facts or summarize
a large amount of data.
The most common type of database is called a
relational database
.
In a relational database, there are multiple tables that have relation-
ships to one another. For example, in a sales database, there might be a
Customers table, an Orders table, and an Order Details table. Because
an individual customer can have multiple orders, and an individual order
can contain multiple items, the details about the customer are stored
separately from the details about the order, and the order line items are
stored separately from both. Figure 6.5 shows these tables and their rela-
tionships in Microsoft Access. Using related tables allows a salesperson
to pull up the customer's shipping and payment information whenever
he or she starts a new order, rather than having to reenter it each time.
Microsoft Access creates relational databases.
relational database
A spreadsheetlike
database that shows how items in a database are
connected or have attributes in common.
A hierarchical type of database has a tree structure in which elements
consist of
nodes
. The database starts from a single point, known as the
parent node. The database branches out and has multiple levels. Items
on a branch are known as child nodes. There may be one or several child
nodes. A
hierarchical database
works by narrowing down a search start-
ing with the entire set of records and successively excluding any that the
search doesn't apply to. Family historians would use a hierarchical view
to see all the descendants of a single ancestor.
node (database)
The point of intersection in
a diagram or in a database; where several items
share a node, the node itself becomes important.
hierarchical database
A way of organizing
data from a single starting point or premise in a
treelike parent and child relationship format. All
records are shown in terms of how they relate to
the originating point at the top of the tree.
How an.Online Store Uses Databases
When you buy something online, the online store uses an application program to manage the purchase process
that will connect to the database to check stock levels. When you arrive at the site and log in, the application
will look for you in the customer database and check that your password and email address match the details
for your account. When you add an item to your shopping cart, a database query is run to check the stock levels
and, if applicable, the application places the requested item in your cart and instructs the database stock level to
decrease by one. When you click Checkout to go the payment page, the site will ask you to confirm or revise your
payment details and then issue a request to your bank for the funds. Assuming the request is accepted, the online
shopping application will confirm your purchase and send you an electronic receipt before issuing an instruction to
the warehouse to send out your goods.
