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Implementing MongoDB $exists and $ne?
The $exists is used to check whethre a filed exists, whereas $ne is for not equal condition. Let us first create a collection with documents −
> db.existsDemo.insertOne({"Name":"Chris","Age":21}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7c3916d78f205348bc650") } > db.existsDemo.insertOne({"Name":"","Age":null}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7c39a6d78f205348bc651") } > db.existsDemo.insertOne({"Name":null,"Age":24}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7c3a66d78f205348bc652") } > db.existsDemo.insertOne({"Age":23}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7c3c36d78f205348bc653") }
Following is the query to display all documents from a collection with the help of find() method −
> db.existsDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5cd7c3916d78f205348bc650"),
"Name" : "Chris",
"Age" : 21
}
{ "_id" : ObjectId("5cd7c39a6d78f205348bc651"), "Name" : "", "Age" : null }
{ "_id" : ObjectId("5cd7c3a66d78f205348bc652"), "Name" : null, "Age" : 24 }
{ "_id" : ObjectId("5cd7c3c36d78f205348bc653"), "Age" : 23 }Following is the query to implement $exists operator −
> db.existsDemo.find({"$and":[ {"Name":{"$exists":true}}, {"Name":{"$ne": ""}}]});
This will produce the following output −
{ "_id" : ObjectId("5cd7c3916d78f205348bc650"), "Name" : "Chris", "Age" : 21 }
{ "_id" : ObjectId("5cd7c3a66d78f205348bc652"), "Name" : null, "Age" : 24 }
Updated on: 30-Jul-2019
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