MongoDB query to update only certain fields?

To update only certain fields, use $set. Let us create a collection with documents −

> db.demo265.insertOne({"id":101,"Name":"Chris"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e480d781627c0c63e7dbaa4")
}
> db.demo265.insertOne({"id":102,"Name":"Bob"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e480d7d1627c0c63e7dbaa5")
}
> db.demo265.insertOne({"id":103,"Name":"David"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e480d841627c0c63e7dbaa6")
}

Display all documents from a collection with the help of find() method −

> db.demo265.find();

This will produce the following output −

{ "_id" : ObjectId("5e480d781627c0c63e7dbaa4"), "id" : 101, "Name" : "Chris" }
{ "_id" : ObjectId("5e480d7d1627c0c63e7dbaa5"), "id" : 102, "Name" : "Bob" }
{ "_id" : ObjectId("5e480d841627c0c63e7dbaa6"), "id" : 103, "Name" : "David" }

Following is the query to update only certain fields −

> db.demo265.update({Name:"David"},{$set:{id:10004}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Display all documents from a collection with the help of find() method −

> db.demo265.find();

This will produce the following output −

{ "_id" : ObjectId("5e480d781627c0c63e7dbaa4"), "id" : 101, "Name" : "Chris" }
{ "_id" : ObjectId("5e480d7d1627c0c63e7dbaa5"), "id" : 102, "Name" : "Bob" }
{ "_id" : ObjectId("5e480d841627c0c63e7dbaa6"), "id" : 10004, "Name" : "David" }