How to update only some properties of object in MongoDB database

In MongoDB, if you want to update specific fields within an object of a document rather than the entire document, you can use the $set operator. This operator enables precise modification of targeted fields without altering other fields.

For example, suppose we have a collection named users containing the following document:

json
{
  "_id": 1,
  "name": "Zhang San",
  "age": 30,
  "address": {
    "city": "Beijing",
    "district": "Chaoyang"
  }
}

Now, we want to update the city field within the user's address, changing it from 'Beijing' to 'Shanghai', without affecting the district field or any other fields. We can use the following MongoDB update operation:

javascript
db.users.updateOne(
  { "_id": 1 },
  { "$set": { "address.city": "Shanghai" } }
);

Here, the updateOne method specifies the document to update (via the _id field), and the $set operator indicates that only the address.city field should be modified. This approach does not impact other properties within the address object or other fields in the document.

This update method is powerful and flexible because it allows you to modify only a portion of the document without sending the entire document back to the database. It is particularly useful when handling large documents or in poor network conditions, as it significantly reduces the amount of data transmitted over the network.