Microsoft Office Tutorials and References
In Depth Information
two digits following the decimal point. Like numeric fi elds, you can use currency
fi elds in arithmetic operations. Access assigns a size to currency fi elds automatically.
Table 1–1 shows the other data types that are available.
Table 1–1 Additional Data Types
Data Type
Description
Memo
Field can store a variable amount of text or combinations of text and numbers where
the total number of characters may exceed 255.
Date/Time
Field can store dates and times.
AutoNumber
Field can store a unique sequential number that Access assigns to a record. Access
will increment the number by 1 as each new record is added.
Yes/No
Field can store only one of two values. The choices are Yes/No, True/False, or On/Off.
OLE Object
Field can store an OLE object, which is an object linked to or embedded in the table.
Hyperlink
Field can store text that can be used as a hyperlink address.
Attachment
Field can contain an attached fi le. Images, spreadsheets, documents, charts, and so
on can be attached to this fi eld in a record in the database. You can view and edit
the attached fi le.
In the Client table, because the Client Number, Client Name, Street, City, and
State can all contain letters, their data types should be Text. The data type for Postal Code
is Text instead of Number, because postal codes are not used in arithmetic operations. You
do not add postal codes or fi nd an average postal code, for example. The Amount Paid and
Current Due fi elds both contain monetary data, so their data types should be Currency.
Similarly, in the Recruiter table, the data type for the Recruiter Number, Last Name,
First Name, Street, City, State, and Postal Code fi elds all should be Text. The Commission
fi eld contains monetary amounts, so its data type should be Currency. The Rate fi eld
contains a number that is not a currency amount, so its data type should be Number.
Identifying and Removing Redundancy
Redundancy means storing the same fact in more than one place. It usually results
from placing too many fi elds in a table — fi elds that really belong in separate tables —
and often causes serious problems. If you had not realized there were two objects, clients
and recruiters, for example, you might have placed all the data in a single Client table.
Figure 1–3 shows a portion of this table with some sample data. Notice that the data for a
given Recruiter (number, name, address, and so on) occurs on more than one record. The
data for Camden Reeves is repeated in the fi gure.
clients of
recruiter 24
name of recruiter 24
appears more than once
Client Table
Client Number
Client Name
Street
Recruiter
Number
Last
Name
First Name
...
...
AC34
Alys Clinic
134 Central
21
Kerry
Alyssa
...
...
BH72
Berls Hospital
415 Main
24
Reeves
Camden
...
...
BL12
Benton Labs
12 Mountain
24
Reeves
Camden
...
...
...
...
...
...
...
...
...
...
Figure 1–3
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