SUMMARY
The information covered in this article is provided by the
Microsoft Press. For more information, visit the following Microsoft Web site:
This article is part 1 of a series of eight
articles that explain how to keep your information in Access accurate. To view
the other articles in this series, see the "Additional resources"
section later in this article.
This information is an excerpt from chapter 6: "Keeping Your Information Accurate" of
the book
Microsoft Access Version 2002 Step by Step. For more information about this book, see the "References" section.
MORE INFORMATION
Depending on how much information you have and how
organized you are, you might compare a database to an old shoebox or a file
cabinet, into which you toss items such as photographs, bills, receipts, and a
variety of other paperwork for later retrieval. However, neither a shoebox nor
a file cabinet restricts what you can place in it (other than how much you can
place in it) or imposes any order on its content. It is up to you to decide
what you store there and to organize it properly so that you can find it when
you next need it. And neither a shoebox nor a file cabinet helps you with the
task of updating your information when it changes or becomes
obsolete.
When you create a database with Microsoft Access, you can
set properties that restrict what can be entered in it, thereby keeping the
database organized and useful. For example, The Garden Company wouldn't want
its employees to enter text into fields that should contain numbers, such as
price fields. Similarly, they wouldn't want to encourage employees to enter a
long text description of something when a simple "yes" or "no" answer would
work best. The field properties that control input are
Required,
Allow Zero Length,
Field Size,
Input Mask, and
Validation Rule. The
Required and
Allow Zero Length properties are fairly obvious. If the
Required property is set to
Yes, the field can't be left blank. However, if
Allow Zero Length is set to
Yes, you can enter an empty
string (two quotation marks with nothing in between), which looks like
an empty field.
TIP: Each property has many options. For more information about how
to use properties, search for
field property in Access online Help.
To ensure the ongoing accuracy
of a database, you can create and run action queries that quickly update
information or delete selected records from a table. For example, The Garden
Company might decide to increase the price of all products in one category by
some percentage, or to remove one entire product line. This type of updating is
easy to do with an action query. Not only does using a query save time, but it
also avoids human input errors.
The exercises in this series of
articles demonstrate how to use the data type and some of the field properties
to restrict the data that can be entered in a table or form. It is difficult to
experiment with field properties in a table that is already filled with
information, because changing a field's data type or properties can destroy or
alter the data.
Additional resources
For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
311167
Part 1 of "Keeping Your Information Accurate": Introduction for Access 2003 and Access 2002
311168 Part 2 of "Keeping Your Information Accurate": Using the data type to restrict data in Access 2003 and Access 2002
311169 Part 3 of "Keeping Your Information Accurate": Using the field size property to restrict data in Access 2003 and Access 2002
311171 Part 4 of "Keeping Your Information Accurate": Using an input mask to restrict data in Access 2003 and Access 2002
311172 Part 5 of "Keeping Your Information Accurate": Using validation rules to restrict data in Access 2003 and Access 2002
311173 Part 6 of "Keeping Your Information Accurate": Using a lookup list to restrict data in Access 2003 and Access 2002
311174 Part 7 of "Keeping Your Information Accurate": Updating information in a table in Access 2003 and Access 2002
311175 Part 8 of "Keeping Your Information Accurate": Deleting information from a table in Access 2003 and Access 2002
REFERENCES
The information in this article is an excerpt from the
Microsoft Access Version 2002 Step by Step book, published by Microsoft Press.
To learn more about
the
Microsoft Access Version 2002 Step by Step book, and to see a sample chapter from this book, visit the following Microsoft Web site:
For more information
about this publication and about other Microsoft Press titles, visit the following Microsoft Web site:
