VBA/Excel/Access/Word/Data Type/Null

How Null Propagates

 
Sub nullDemo()
    Dim varFirstName   As Variant
    Dim varLastName   As Variant
    Dim varFullName   As Variant
    
    varFirstName = "Janine"
    varLastName = Null
    
    varFullName = varFirstName & varLastName
     
    Debug.Print varFullName
End Sub

Nulls are not equal

 
Sub CompareNulls()
    
    Dim varValue1 As Variant
    Dim varValue2 As Variant
    
    varValue1 = Null
    varValue2 = Null
    
    If varValue1 = varValue2 Then
        Debug.Print "Nulls are not equal"
    End If
End Sub

use IsNull function to check

 
Sub CompareNulls2()
    Dim varValue1 As Variant
    Dim varValue2 As Variant
    
    varValue1 = Null
    varValue2 = Null
    
    If IsNull(varValue1) And IsNull(varValue2) Then
        Debug.Print "Both variables are Null"
    End If
    
End Sub