Retrieving the first document in a MongoDB collection?

To retrieve the first document in a collection, you can use findOne(). Following is the syntax

var anyVariableName=db.yourCollectionName.findOne();
//To print result at MongoDB console write the variable name
yourVariableName

Let us first create a collection with documents

> db.retrieveFirstDocumentDemo.insertOne({"ClientName":"Robert","ClientAge":23});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ca2325966324ffac2a7dc6d")
}
> db.retrieveFirstDocumentDemo.insertOne({"ClientName":"Chris","ClientAge":26});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ca2326266324ffac2a7dc6e")
}
> db.retrieveFirstDocumentDemo.insertOne({"ClientName":"Larry","ClientAge":29});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ca2326a66324ffac2a7dc6f")
}
> db.retrieveFirstDocumentDemo.insertOne({"ClientName":"David","ClientAge":39});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ca2327566324ffac2a7dc70")
}

Following is the query to display all documents from a collection with the help of find() method

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

This will produce the following output

{
   "_id" : ObjectId("5ca2325966324ffac2a7dc6d"),
   "ClientName" : "Robert",
   "ClientAge" : 23
}
{
   "_id" : ObjectId("5ca2326266324ffac2a7dc6e"),
   "ClientName" : "Chris",
   "ClientAge" : 26
}
{
   "_id" : ObjectId("5ca2326a66324ffac2a7dc6f"),
   "ClientName" : "Larry",
   "ClientAge" : 29
}
{
   "_id" : ObjectId("5ca2327566324ffac2a7dc70"),
   "ClientName" : "David",
   "ClientAge" : 39
}

Following is the query to retrieve first document in a collection

> var firstDocumentOnly=db.retrieveFirstDocumentDemo.findOne();
> firstDocumentOnly;

This will produce the following output

{
   "_id" : ObjectId("5ca2325966324ffac2a7dc6d"),
   "ClientName" : "Robert",
   "ClientAge" : 23
}