How to update a single field in a capped collection in MongoDB?

To update, you need to use update() for the field whose collection is set with capped: true. Let us create a collection with documents −

> db.createCollection("Demo112", { capped : true, size : 14, max : 3 } );
{ "ok" : 1 }
> db.demo112.insertOne({"Name":"Chris"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e2ef47a9fd5fd66da21447e")
}
> db.demo112.insertOne({"Name":"David"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e2ef47e9fd5fd66da21447f")
}
> db.demo112.insertOne({"Name":"David"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e2ef4919fd5fd66da214480")
}

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

> db.demo112.find();

This will produce the following output −

{ "_id" : ObjectId("5e2ef47a9fd5fd66da21447e"), "Name" : "Chris" }
{ "_id" : ObjectId("5e2ef47e9fd5fd66da21447f"), "Name" : "David" }
{ "_id" : ObjectId("5e2ef4919fd5fd66da214480"), "Name" : "David" }

Following is the query to update a single field in a capped collection −

> db.demo112.update(
...    {Name:"David"},
...    {$set:{Name: "Robert"}},
...    {multi:true}
... )
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })

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

> db.demo112.find();

This will produce the following output −

{ "_id" : ObjectId("5e2ef47a9fd5fd66da21447e"), "Name" : "Chris" }
{ "_id" : ObjectId("5e2ef47e9fd5fd66da21447f"), "Name" : "Robert" }
{ "_id" : ObjectId("5e2ef4919fd5fd66da214480"), "Name" : "Robert" }