Microsoft Office Tutorials and References
In Depth Information
Field Properties for Making Sure That Data Entries Are Accurate
If someone enters data that violates a validation rule that you enter in the
Validation Rule text box, Access displays a standard error message. The
message reads, “One or more values are prohibited by the validation rule set
for [this field]. Enter a value that the expression for this field can accept.” If
this message is too cold and impersonal for you, you can create a message
of your own for the error message dialog box. Enter your friendly message in
the Validation Text text box.
By default, no entry has to be made in a field, but if you choose Yes instead
of No in the Required box and you fail to make an entry in the field, a
message box tells you to be sure to make an entry.
Allow Zero Length
This property allows you to enter zero-length strings in a field. A zero-length
string — two quotation marks with no text or spaces between them (“”) —
indicates that no value exists for a field. To see how zero-length strings work,
suppose that your database table calls for entering e-mail addresses. If you
didn’t know whether one person has an e-mail address, you would leave the
E-Mail Address field blank. If, however, you knew that the person didn’t have
an e-mail address, you could indicate as much by entering a zero-length string.
Choose Yes on the drop-down list to permit zero-length strings to be entered
in the field.
Indicates that the field has been indexed. As “Indexing for Faster Sorts,
Searches, and Queries” explains later in this chapter, indexes make sorting
a field and searching through a field go faster. The word No appears in this
text box if the field has not been indexed.
Choose Yes from the Unicode Expression drop-down list if you want to
compress data that is now stored in Unicode format. Storing data this way saves
on disk space, and you probably don’t want to change this property.
If you intend to enter Smart Tags in the field, indicate which kind you enter
by clicking the three dots next to the Smart Tags box and choosing an option
in the Action Tags dialog box.