$unset

Definition

$unset

The $unset operator deletes a particular field.

Compatibility

You can use $unset for deployments hosted in the following environments:

• MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

• MongoDB Enterprise: The subscription-based, self-managed version of MongoDB

• MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Syntax

Consider the following syntax:

{ $unset: { <field1>: "", ... } }

The specified value in the $unset expression (i.e. "") does not impact the operation.

To specify a <field> in an embedded document or in an array, use dot notation.

Behavior

In MongoDB 4.4 and earlier, update operators process document fields in lexicographic order. See Update Operators Behavior for details.

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.

Example

The following update() operation uses the $unset operator to remove the fields quantity and instock from the first document in the products collection where the field sku has a value of unknown.

db.products.update(
   { sku: "unknown" },
   { $unset: { quantity: "", instock: "" } }
)