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How do I check whether a field contains null value in MongoDB?
You can use $type operator to check whether a filed contains null value. Let us first create a collection with documents. We have also inserted a null in a field −
> db.nullDemo.insertOne({"FirstName":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cc68a1eac184d684e3fa270")
}
> db.nullDemo.insertOne({"FirstName":null});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cc68a25ac184d684e3fa271")
}
> db.nullDemo.insertOne({"FirstName":"Robert"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cc68a2cac184d684e3fa272")
}Following is the query to display all documents from a collection with the help of find() method −
> db.nullDemo.find().pretty();
This will produce the following output. One of the field is null −
{ "_id" : ObjectId("5cc68a1eac184d684e3fa270"), "FirstName" : "Chris" }
{ "_id" : ObjectId("5cc68a25ac184d684e3fa271"), "FirstName" : null }
{ "_id" : ObjectId("5cc68a2cac184d684e3fa272"), "FirstName" : "Robert" }Here is the query to check whether a field contains null value. The field “FirstName” is checked −
> db.nullDemo.find( { FirstName: { $type: 10 } } );This will produce the following output −
{ "_id" : ObjectId("5cc68a25ac184d684e3fa271"), "FirstName" : null }
Updated on: 30-Jul-2019
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