MongoDB query by sub-field?

You can use dot(.) notation to query by subfield. Let us create a collection with a document. The query to create a collection with a document is as follows −

> db.queryBySubFieldDemo.insertOne(    ... {       ... "StudentPersonalDetails" : {"StudentName" : "John","StudentHobby" :"Photography"},       ... "StudentScores" : {"MathScore" : 56}    ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5c92c2995259fcd195499808") } > db.queryBySubFieldDemo.insertOne(    ... {       ... "StudentPersonalDetails" : {"StudentName" : "Chris","StudentHobby" :"Reading"},       ... "StudentScores" : {"MathScore" : 97}    ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5c92c2df5259fcd195499809") }

Display all documents from a collection with the help of find() method. The query is as follows −

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

The following is the output −

{    "_id" : ObjectId("5c92c2995259fcd195499808"),    "StudentPersonalDetails" : {       "StudentName" : "John",       "StudentHobby" : "Photography"    },    "StudentScores" : {       "MathScore" : 56    } } {    "_id" : ObjectId("5c92c2df5259fcd195499809"),    "StudentPersonalDetails" : {       "StudentName" : "Chris",       "StudentHobby" : "Reading"    },    "StudentScores" : {       "MathScore" : 97    } }

Here is the query by subfield −

> db.queryBySubFieldDemo.find({"StudentPersonalDetails.StudentName":"Chris"}).pretty();

The following is the output −

{    "_id" : ObjectId("5c92c2df5259fcd195499809"),    "StudentPersonalDetails" : {       "StudentName" : "Chris",       "StudentHobby" : "Reading"    },    "StudentScores" : {       "MathScore" : 97    } }