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Null Function

This standard VB function sets a variant variable to the Null value.

Syntax

Null

Returns

A variant value set to NULL.

Usage

Null is used to set a variant variable to the Null value explicitly, as follows:

variableName = Null

Note that variants are initialized by Basic to the empty value, which is different from the Null value.

Example

This example asks for ten test score values and calculates the average. If any score is negative, the value is set to Null. Then IsNull is used to reduce the total count of scores (originally 10) to just those with positive values before calculating the average.

Sub Button_Click
   Dim arrayvar(10)
   Dim count as Integer
   Dim total as Integer
   Dim x as Integer
   Dim tscore as Single
   count = 10
   total = 0
   For x = 1 to count
      tscore = 88
      If tscore < 0 then
         arrayvar(x) = Null
      Else
         arrayvar(x) = tscore
         total = total + arrayvar(x)
      End If
   Next x
   Do While x <> 0
      x = x - 1
      If IsNull(arrayvar(x)) = -1 then
         count = count - 1
      End If
   Loop
   msgtext = " The average (excluding negative values) is: "
      msgtext = msgtext & Chr(10) & Format (total/count, "##.##")
End Sub

See Also

IsEmpty Function
IsNull Function
VarType Function