Checks a value to see if it is $Null.
expression IS [NOT] $NULL
| expression | Any expression. |
Logical.
An IS $NULL comparison is logically true if expression is valueless (unassigned). If expression has been assigned any value (including the null string), then the comparison is logically false.
An IS NOT $NULL comparison is logically true if expression has been assigned any value (including the null string). If expression is valueless (unassigned), then the comparison is logically false.
$NULL can also be written as NULL.
To find all employees whose records have no value recorded in the Age field, and then change that value to 39, enter
change all Employees where Age is $Null let Age = 39