Database Reference
In-Depth Information
You can combine these basic operators to form the following:
<= Less than or equal to
>= Greater than or equal to
<> Not equal to
The Like operator is sometimes grouped with the comparison operators and is used
to test whether or not text matches a pattern.
Arithmetic operators
+ Add
- Subtract
* Multiply
/ Divide
A related operator, & (a text form of +) is used to concatenate (combine) two text
strings.
6
You can enter validation rules in the Validation Rule property box by hand, or you can use
a tool called the Expression Builder to create them. The Expression Builder isn't a wizard; it
doesn't lead you through the process of building an expression. It provides a hierarchical
list of common elements that you might want to include in an expression, and an expres-
sion box to build the expression in. To open the Expression Builder dialog box, click the
Validation button in the Field Validation group on the Fields tool tab, and then click either
Field Validation Rule or Validation Rule. In the dialog box, either select functions, operators,
and other elements from the list to copy them into the expression box, or enter the expres-
sion directly in the expression box.
To explain a validation rule to users, you can create a message that appears if someone
tries to enter an invalid value. A well-crafted message tells users what data is expected
and what format it should be entered in. For example, the message Please enter a whole
number between 1 and 99 is more useful than Invalid entry .
 
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