$unsetoperator deletes a particular field. Consider the following syntax:
The specified value in the
"") does not impact the operation.
To specify a
<field>in an embedded document or in an array, use dot notation.
If the field does not exist, then
$unset does nothing (i.e. no operation).
When used with
$ to match an array element,
$unset replaces the matching element with
null rather than removing the matching element from the array. This behavior keeps consistent the array size and element positions.