Search for documents matching first item in an array with MongoDB?

Let us first create a collection with documents −

> db.matchingFirstItemInTheArrayDemo.insertOne(    {       "ClientDetails": [          {             "ClientName": "Larry",             "ClientAge":28          }       ]    } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd7a5d26d78f205348bc636") } > db.matchingFirstItemInTheArrayDemo.insertOne( {    "ClientDetails": [       {          "ClientName": "Chris",          "ClientAge":56,       }    ] } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd7a5f56d78f205348bc637") } > db.matchingFirstItemInTheArrayDemo.insertOne(    {       "ClientDetails": [          {             "ClientName": "Robert",             "ClientAge":46,          }       ]    } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd7a6076d78f205348bc638") }

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

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

This will produce the following output −

{    "_id" : ObjectId("5cd7a5d26d78f205348bc636"),    "ClientDetails" : [       {          "ClientName" : "Larry",          "ClientAge" : 28       }    ] } {    "_id" : ObjectId("5cd7a5f56d78f205348bc637"),    "ClientDetails" : [       {          "ClientName" : "Chris",          "ClientAge" : 56       }    ] } {    "_id" : ObjectId("5cd7a6076d78f205348bc638"),    "ClientDetails" : [       {          "ClientName" : "Robert",          "ClientAge" : 46       }    ] }

Following is the query to search for documents matching first item in array −

> db.matchingFirstItemInTheArrayDemo.find({"ClientDetails.0.ClientName":"Chris"});

This will produce the following output −

{ "_id" : ObjectId("5cd7a5f56d78f205348bc637"), "ClientDetails" : [ { "ClientName" : "Chris", "ClientAge" : 56 } ] }