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I want to create a new field in an already created document. How can this be done using MongoDB query?
Use $addToSet to create a new field in MongoDB. Let us first create a collection with documents −
> db.createFieldDemo.insertOne({"StudentFirstName":"John","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e28b50a6c6dd317ad95")
}
> db.createFieldDemo.insertOne({"StudentFirstName":"Larry","StudentAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e2fb50a6c6dd317ad96")
}
> db.createFieldDemo.insertOne({"StudentFirstName":"Chris","StudentAge":22});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e38b50a6c6dd317ad97")
}
> db.createFieldDemo.insertOne({"StudentFirstName":"David","StudentAge":25});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e43b50a6c6dd317ad98")
}Following is the query to display all documents from a collection with the help of find() method −
> db.createFieldDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5cd99e28b50a6c6dd317ad95"),
"StudentFirstName" : "John",
"StudentAge" : 21
}
{
"_id" : ObjectId("5cd99e2fb50a6c6dd317ad96"),
"StudentFirstName" : "Larry",
"StudentAge" : 23
}
{
"_id" : ObjectId("5cd99e38b50a6c6dd317ad97"),
"StudentFirstName" : "Chris",
"StudentAge" : 22
}
{
"_id" : ObjectId("5cd99e43b50a6c6dd317ad98"),
"StudentFirstName" : "David",
"StudentAge" : 25
}Following is the query to create a new field. Here, we are creating a field “StudentLastName” −
> db.createFieldDemo.update({_id: ObjectId("5cd99e43b50a6c6dd317ad98")}, {$addToSet: {"StudentLastName": "Miller"}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Let us check all documents from the above collection −
> db.createFieldDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5cd99e28b50a6c6dd317ad95"),
"StudentFirstName" : "John",
"StudentAge" : 21
}
{
"_id" : ObjectId("5cd99e2fb50a6c6dd317ad96"),
"StudentFirstName" : "Larry",
"StudentAge" : 23
}
{
"_id" : ObjectId("5cd99e38b50a6c6dd317ad97"),
"StudentFirstName" : "Chris",
"StudentAge" : 22
}
{
"_id" : ObjectId("5cd99e43b50a6c6dd317ad98"),
"StudentFirstName" : "David",
"StudentAge" : 25,
"StudentLastName" : [
"Miller"
]
}
Updated on: 30-Jul-2019
40 Views
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