None
None returns true
if none of the specified fields contain a value
If None(fieldname
or variable) then
All
Use the All
function to verify if a field contains a value, or if all the fields in a list
of fields contain values. If any of the fields are Null, then All returns False.
If All (fieldname or variable)
then
NULL
If you want to
check whether object is null, or it is valid object or not
If object = null then
