Return all ages records that are ints with a MongoDB query

To get all the ages that are ints from records having string and int ages records, use $type. The $type in MongoDB $type selects documents where the value of the field is an instance of the specified BSON type.

Let us create a collection with documents −

> db.demo470.insertOne({"Age":23});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e805456b0f3fa88e2279070")
}
> db.demo470.insertOne({"Age":"Unknown"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e80545cb0f3fa88e2279071")
}
> db.demo470.insertOne({"Age":24});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e805461b0f3fa88e2279072")
}
> db.demo470.insertOne({"Age":"Not provided"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e80546bb0f3fa88e2279073")
}

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

> db.demo470.find();

This will produce the following output −

{ "_id" : ObjectId("5e805456b0f3fa88e2279070"), "Age" : 23 }
{ "_id" : ObjectId("5e80545cb0f3fa88e2279071"), "Age" : "Unknown" }
{ "_id" : ObjectId("5e805461b0f3fa88e2279072"), "Age" : 24 }
{ "_id" : ObjectId("5e80546bb0f3fa88e2279073"), "Age" : "Not provided" }

Following is the query to return all ages that are ints −

> db.demo470.find( {'Age' : { $type :"number"} } );

This will produce the following output −

{ "_id" : ObjectId("5e805456b0f3fa88e2279070"), "Age" : 23 }
{ "_id" : ObjectId("5e805461b0f3fa88e2279072"), "Age" : 24 }