MongoDB Projection Result as an Array of Selected Items

Let us create a collection with documents −

> db.demo151.insertOne({"ListOfNames":["Chris","David","Mike"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e3513b6fdf09dd6d08539da")
}
> db.demo151.insertOne({"ListOfNames":["Mike","Bob"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e3513c4fdf09dd6d08539db")
}
> db.demo151.insertOne({"ListOfNames":["John","David","Chris"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e3513dcfdf09dd6d08539dc")
}

Display all documents from a collection with the help of find() method −

> db.demo151.find();

This will produce the following output −

{ "_id" : ObjectId("5e3513b6fdf09dd6d08539da"), "ListOfNames" : [ "Chris", "David", "Mike" ] }
{ "_id" : ObjectId("5e3513c4fdf09dd6d08539db"), "ListOfNames" : [ "Mike", "Bob" ] }
{ "_id" : ObjectId("5e3513dcfdf09dd6d08539dc"), "ListOfNames" : [ "John", "David", "Chris" ] }

Following is the query to projection result as an array of selected items −

> db.demo151.distinct('_id', {'ListOfNames' : "Mike"});

This will produce the following output −

[
   ObjectId("5e3513b6fdf09dd6d08539da"),
   ObjectId("5e3513c4fdf09dd6d08539db")
]