Getting only the first item for an array property in MongoDB?

Use $slice operator for this. Let us first create a collection with documents −

> db.gettingFirstItemInArrayDemo.insertOne(    {       "UserId": 101,       "UserName":"Carol",       "UserOtherDetails": [          {"UserFriendName":"Sam"},          {"UserFriendName":"Mike"},          {"UserFriendName":"David"},          {"UserFriendName":"Bob"}       ]    } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5cdfca52bf3115999ed51205") }

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

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

This will produce the following output −

{    "_id" : ObjectId("5cdfca52bf3115999ed51205"),    "UserId" : 101,    "UserName" : "Carol",    "UserOtherDetails" : [       {          "UserFriendName" : "Sam"       },       {          "UserFriendName" : "Mike"       },       {          "UserFriendName" : "David"       },       {          "UserFriendName" : "Bob"       }    ] }

Following is the query to get only the first item for an array property in MongoDB −

> db.gettingFirstItemInArrayDemo.find({"UserId":101}, {UserOtherDetails:{$slice: 1}});

This will produce the following output −

{ "_id" : ObjectId("5cdfca52bf3115999ed51205"), "UserId" : 101, "UserName" : "Carol", "UserOtherDetails" : [ { "UserFriendName" : "Sam" } ] }