Microsoft Office Tutorials and References
In Depth Information
Databases and Relationships
A collection of related tables is called a database , or a relational database . NSJI’s Seasonal
database contains two related tables: the Employer and NAICS tables, which Elsa created.
(The NAICS table contains North American Industry Classification System codes, which are
used to classify businesses according to their activities.) In Tutorial 2, you will create a
Position table to store information about the available positions at NSJI’s employer clients.
Sometimes you might want information about employers and their available positions.
To obtain this information, you must have a way to connect records in the Employer table
to records in the Position table. You connect the records in the separate tables through a
common field that appears in both tables.
In the sample database shown in Figure 1-2, each record in the Employer table has a
field named EmployerID, which is also a field in the Position table. For example, BaySide
Inn & Country Club is the third employer in the Employer table and has an EmployerID
field value of 10126. This same EmployerID field value, 10126, appears in three records
in the Position table. Therefore, BaySide Inn & Country Club is the employer with these
three positions available.
Database relationship between tables for employers and positions
105 State Street, Boston, MA 02109
75 Atlantic Avenue, Boston, MA 02110
Boston Harbor Excursions
BaySide Inn & Country Club
354 Oceanside Drive, Brewster, MA 02631
The Briar Rose Inn
105 Queen Street, Charlottetown PE C1A 8R4
Windsor Alpine Tours
14 Longmeadow Road, Laconia, NH 03246
Trudel Spa & Resort
40 Rue Rivard, North Hatley QC J0B 2C0
for BaySide Inn &
Pro Shop Clerk
Each EmployerID value in the Employer table must be unique, so that you can distin-
guish one employer from another and identify the employer’s specific positions available
in the Position table. The EmployerID field is referred to as the primary key of the
Employer table. A primary key is a field, or a collection of fields, whose values uniquely
identify each record in a table. In the Position table, PositionID is the primary key.