MongoDB - update partial number of documents?

To update partial number of documents, set multi to true. Let us create a collection with documents −

> db.demo312.insertOne({"FirstName":"Robert"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e50ce16f8647eb59e56204a")
}
> db.demo312.insertOne({"FirstName":"Bob"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e50ce19f8647eb59e56204b")
}
> db.demo312.insertOne({"FirstName":"Robert"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e50ce1cf8647eb59e56204c")
}
> db.demo312.insertOne({"FirstName":"David"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e50ce20f8647eb59e56204d")
}
> db.demo312.insertOne({"FirstName":"Robert"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e50ce22f8647eb59e56204e")
}

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

> db.demo312.find();

This will produce the following output −

{ "_id" : ObjectId("5e50ce16f8647eb59e56204a"), "FirstName" : "Robert" }
{ "_id" : ObjectId("5e50ce19f8647eb59e56204b"), "FirstName" : "Bob" }
{ "_id" : ObjectId("5e50ce1cf8647eb59e56204c"), "FirstName" : "Robert" }
{ "_id" : ObjectId("5e50ce20f8647eb59e56204d"), "FirstName" : "David" }
{ "_id" : ObjectId("5e50ce22f8647eb59e56204e"), "FirstName" : "Robert" }

Following is the query to update partial number of documents

> db.demo312.update({"FirstName":"Robert"},{$set:{"FirstName":"Sam"}},{multi:true});
WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })

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

> db.demo312.find();

This will produce the following output −

{ "_id" : ObjectId("5e50ce16f8647eb59e56204a"), "FirstName" : "Sam" }
{ "_id" : ObjectId("5e50ce19f8647eb59e56204b"), "FirstName" : "Bob" }
{ "_id" : ObjectId("5e50ce1cf8647eb59e56204c"), "FirstName" : "Sam" }
{ "_id" : ObjectId("5e50ce20f8647eb59e56204d"), "FirstName" : "David" }
{ "_id" : ObjectId("5e50ce22f8647eb59e56204e"), "FirstName" : "Sam" }