Find documents that contains specific field in MongoDB?

For this, use the $exists operator. Let us first create a collection with documents −

>dbfindDocumentContainsSpecificFieldDemoinsertOne({"ProductPrices":{"Product1":10,"Pr oduct2":50}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cf2385bb64a577be5a2bc14") } >dbfindDocumentContainsSpecificFieldDemoinsertOne({"ProductPrices":{"Product3":150,"P roduct7":100,"Product5":250}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cf2387eb64a577be5a2bc15") }

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

> dbfindDocumentContainsSpecificFieldDemofind()pretty();

This will produce the following document −

{    "_id" : ObjectId("5cf2385bb64a577be5a2bc14"),    "ProductPrices" : {       "Product1" : 10,       "Product2" : 50    } } {    "_id" : ObjectId("5cf2387eb64a577be5a2bc15"),    "ProductPrices" : {       "Product3" : 150,       "Product7" : 100,       "Product5" : 250    } }

Following is the query to find documents that contains specific field −

> dbfindDocumentContainsSpecificFieldDemofind({"ProductPricesProduct2":{$exists:true}});

This will produce the following document −

{ "_id" : ObjectId("5cf2385bb64a577be5a2bc14"), "ProductPrices" : { "Product1" : 10, "Product2" : 50 } }