To add new field to every document in a MongoDB collection, you can use $set operator. The syntax is as follows:
db.yourCollectionName.update({}, { $set: {"yourFieldName": yourValue} }, false, true);
To understand the above syntax, let us create a collection with some documents. The query to create a collection with documents is as follows:
>db.addNewFieldToEveryDocument.insertOne({"StudentName":"John","StudentAddress":"US "}); { "acknowledged" : true, "insertedId" : ObjectId("5c6efc0b6fd07954a48906ae") } >db.addNewFieldToEveryDocument.insertOne({"StudentName":"David","StudentAddress":"U K"}); { "acknowledged" : true, "insertedId" : ObjectId("5c6efc0b6fd07954a48906af") } >db.addNewFieldToEveryDocument.insertOne({"StudentName":"Carol","StudentAddress":"U K"}); { "acknowledged" : true, "insertedId" : ObjectId("5c6efc0b6fd07954a48906b0") } >db.addNewFieldToEveryDocument.insertOne({"StudentName":"Bob","StudentAddress":"US" }); { "acknowledged" : true, "insertedId" : ObjectId("5c6efc0b6fd07954a48906b1") }
Display all documents from a collection with the help of find() method. The query is as follows:
> db.addNewFieldToEveryDocument.find().pretty();
The following is the output:
{ "_id" : ObjectId("5c6efc0b6fd07954a48906ae"), "StudentName" : "John", "StudentAddress" : "US" } { "_id" : ObjectId("5c6efc0b6fd07954a48906af"), "StudentName" : "David", "StudentAddress" : "UK" } { "_id" : ObjectId("5c6efc0b6fd07954a48906b0"), "StudentName" : "Carol", "StudentAddress" : "UK" } { "_id" : ObjectId("5c6efc0b6fd07954a48906b1"), "StudentName" : "Bob", "StudentAddress" : "US" }
The following is the query to add a new field to every document:
> db.addNewFieldToEveryDocument.update({}, { $set: {"StudentAge": 24} }, false, true); WriteResult({ "nMatched" : 4, "nUpserted" : 0, "nModified" : 4 })
Above, we have added a new field “StudentAge”:24 in every document. Let us check the field “StudentAge”:24 is successfully added to every document or not. The query is as follows:
> db.addNewFieldToEveryDocument.find().pretty();
The following is the output:
{ "_id" : ObjectId("5c6efc0b6fd07954a48906ae"), "StudentName" : "John", "StudentAddress" : "US", "StudentAge" : 24 } { "_id" : ObjectId("5c6efc0b6fd07954a48906af"), "StudentName" : "David", "StudentAddress" : "UK", "StudentAge" : 24 } { "_id" : ObjectId("5c6efc0b6fd07954a48906b0"), "StudentName" : "Carol", "StudentAddress" : "UK", "StudentAge" : 24 } { "_id" : ObjectId("5c6efc0b6fd07954a48906b1"), "StudentName" : "Bob", "StudentAddress" : "US", "StudentAge" : 24 }