Description
Evaluates the field specified in the previous record and returns TRUE if the field contains a null value.
Arguments
fld is any numeric, formula, memo, or BLOB field in the report.
Action
Evaluates the field specified in the previous record and returns TRUE if the field contains a null value.
Typical uses
You can use this function to test for the first item in a list and to take some action when that first item is identified.
Examples
If PreviousIsNull ({employee.EMPLOYEE ID}) Then
"First employee of record"
Else
""
In an employee database with no null values in the Employee ID field, flags the first employee on the list.
Comments
Some databases support null data values and others do not. This function will not work if the active database(s) do not support null values. If the database(s) do support null values, the function can be used to reference the null values that get created as the result of a failed lookup while joining.
Zero and blank (empty or " ") are not null values.
Using this function in a formula forces the formula to be evaluated at print time. For more information on evaluation time considerations, see
Evaluation Time.