How can I search a collection to find a nested value in one of its documents in MongoDB?

For this, use double underscore( __) in find(). Let us first create a collection with documents −

> db.nestedDemo.insertOne({"Information":{"__StudentName":"John Smith"}});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e06f39125ddae1f53b621f0")
}
> db.nestedDemo.insertOne({"Information":{"__StudentName":"John Doe"}});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e06f39e25ddae1f53b621f1")
}
> db.nestedDemo.insertOne({"Information":{"__StudentName":"Chris Brown"}});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e06f3a625ddae1f53b621f2")
}

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

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

This will produce the following output −

{
   "_id" : ObjectId("5e06f39125ddae1f53b621f0"),
   "Information" : {
      "__StudentName" : "John Smith"
   }
}
{
   "_id" : ObjectId("5e06f39e25ddae1f53b621f1"),
   "Information" : {
      "__StudentName" : "John Doe"
   }
}
{
   "_id" : ObjectId("5e06f3a625ddae1f53b621f2"),
   "Information" : {
      "__StudentName" : "Chris Brown"
   }
}

Here is the query to search a collection to find a nested value in one of its documents in MongoDB −

> db.nestedDemo.find({"Information.__StudentName":"John Doe"});

This will produce the following output −

{ "_id" : ObjectId("5e06f39e25ddae1f53b621f1"), "Information" : { "__StudentName" : "John Doe" } }