How to select a single field in MongoDB?

MongoDBDatabaseBig Data Analytics

You can select a single field in MongoDB using the following syntax:

db.yourCollectionName.find({"yourFieldName":yourValue},{"yourSingleFieldName":1,_id:0});

In the above syntax "yourSingleFieldName":1, _id:0 means get all data from one field without _id.

To understand the above syntax, let us create a collection with document. The query to create a collection with document is as follows:

> db.singleFieldDemo.insertOne({"StudentName":"David","StudentAge":28});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c6eba356fd07954a489067c")
}
> db.singleFieldDemo.insertOne({"StudentName":"Bob","StudentAge":18});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c6eba406fd07954a489067d")
}
> db.singleFieldDemo.insertOne({"StudentName":"Chris","StudentAge":24});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c6eba4c6fd07954a489067e")
}
> db.singleFieldDemo.insertOne({"StudentName":"Robert","StudentAge":26});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c6eba586fd07954a489067f")
}

Now you can display all documents from a collection with the help of find() method. The query is as follows:

> db.singleFieldDemo.find().pretty();

The following is the output:

{
   "_id" : ObjectId("5c6eba356fd07954a489067c"),
   "StudentName" : "David",
   "StudentAge" : 28
}
{
   "_id" : ObjectId("5c6eba406fd07954a489067d"),
   "StudentName" : "Bob",
   "StudentAge" : 18
}
{
   "_id" : ObjectId("5c6eba4c6fd07954a489067e"),
   "StudentName" : "Chris",
   "StudentAge" : 24
}
{
   "_id" : ObjectId("5c6eba586fd07954a489067f"),
   "StudentName" : "Robert",
   "StudentAge" : 26
}

Here is the query to select a single field:

> db.singleFieldDemo.find({"StudentAge":18},{"StudentName":1,"_id":0});

The following is the output:

{ "StudentName" : "Bob" }
raja
Published on 18-Mar-2019 11:57:36
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