$set (original) (raw)

Note

Disambiguation

The following page refers to the update operator $set. For the aggregation stage, see $set.

$set

The $set operator replaces the value of a field with the specified value.

You can use $set 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

The $set operator expression has the following form:


{ $set: { <field1>: <value1>, ... } }

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

Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order. See Update Operators Behavior for details.

If the field does not exist, $set will add a new field with the specified value, provided that the new field does not violate a type constraint. If you specify a dotted path for a non-existent field,$set will create the embedded documents as needed to fulfill the dotted path to the field.

If you specify multiple field-value pairs, $set will update or create each field.

Starting in MongoDB 5.0, mongod no longer raises an error when you use an update operator like $setwith an empty operand expression ( { } ). An empty update results in no changes and no oplog entry is created (meaning that the operation is a no-op).

Create the products collection:


db.products.insertOne(

   {

     _id: 100,

     quantity: 250,

     instock: true,

     reorder: false,

     details: { model: "14QQ", make: "Clothes Corp" },

     tags: [ "apparel", "clothing" ],

     ratings: [ { by: "Customer007", rating: 4 } ]

   }

)

For the document matching the criteria _id equal to 100, the following operation uses the $set operator to update the value of the quantity field, details field, and the tagsfield.


db.products.updateOne(

   { _id: 100 },

   { $set:

      {

        quantity: 500,

        details: { model: "2600", make: "Fashionaires" },

        tags: [ "coats", "outerwear", "clothing" ]

      }

   }

)

The operation updates the:

value of quantity to 500
details field with new embedded document
tags field with new array


{

  _id: 100,

  quantity: 500,

  instock: true,

  reorder: false,

  details: { model: '2600', make: 'Fashionaires' },

  tags: [ 'coats', 'outerwear', 'clothing' ],

  ratings: [ { by: 'Customer007', rating: 4 } ]

}

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

For the document matching the criteria _id equal to 100, the following operation updates the make field in the detailsdocument:


db.products.updateOne(

   { _id: 100 },

   { $set: { "details.make": "Kustom Kidz" } }

)

After updating, the document has the following values:


{

   _id: 100,

   quantity: 500,

   instock: true,

   reorder: false,

   details: { model: '2600', make: 'Kustom Kidz' },

   tags: [ 'coats', 'outerwear', 'clothing' ],

   ratings: [ { by: 'Customer007', rating: 4 } ]

}

Important

The above code uses dot notation to update the make field of the embedded details document. The code format looks similar to the following code example, which instead replaces the entire embedded document, removing all other fields in the embedded details document:


db.products.updateOne(

   { _id: 100 },

   { $set: { details:

      {make: "Kustom Kidz"}

      }

   })

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

For the document matching the criteria _id equal to 100, the following operation updates the value second element (array index of1) in the tags field and the rating field in the first element (array index of 0) of the ratings array.


db.products.updateOne(

   { _id: 100 },

   { $set:

      {

        "tags.1": "rain gear",

        "ratings.0.rating": 2

      }

   }

)

After updating, the document has the following values:


{

  _id: 100,

  quantity: 500,

  instock: true,

  reorder: false,

  details: { model: '2600', make: 'Kustom Kidz' },

  tags: [ 'coats', 'rain gear', 'clothing' ],

  ratings: [ { by: 'Customer007', rating: 2 } ]

}

For additional update operators for arrays, seeArray Update Operators.