User manual

72 | Creating databases
3. Once you’ve determined the broad categories, consider how these
categories are related. This can be done by writing simple sentences that
describe how the categories interact, such as, “teachers teach classes,”
“students are assigned to classes,” and “students complete assignments.”
Each of these pairs suggests a relationship between the data in one category
and the data in the other category.
4. Once you’ve identified your categories of information, you are ready to
organize your database.
In database terminology, these categories of information are referred to as
tables. Tables are used to group data containing a common element or
purpose. For example, you might use one table to store names and
addresses, while you use another table to store transaction details, such as
date of sale, item number, unit price, and so on.
Typically, databases are organized in one of three ways:
1 A single table in a single file. Use a single table if you need to track data
in one category only, such as names and addresses.
1 Multiple tables in a single file. Use multiple tables if your data is more
complex, such as students, classes, and grades.
1 Multiple tables in multiple files. Use multiple files if you need to share
the same data among several different database solutions. For example,
you can store your tax rates or shipping information in a separate file if
you plan to use that information in more than one solution.
Note Use relationships to share data between tables in the same file or with
tables in external files. Other database elements, such as scripts and access
privileges, are stored at the file level; therefore, some complex solutions will
benefit from using multiple files.
φμπ10_υσερσ_γυιδε.βοοκ Παγε 72 Μονδαψ, Αυγυστ 25, 2008 3:59 ΠΜ