# How to find a document by the non-existence of a field in MongoDB?

MongoDBDatabaseBig Data Analytics

To find a document by the non-existence of a field in MongoDB, the syntax is as follows −

db.yourCollectionName.find({ "yourFieldName" : { "$exists" : false } }).pretty(); To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows − > db.findDocumentNonExistenceFieldDemo.insertOne({"StudentName":"John","StudentAge":25}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a5c629064dcd4a68b70e8") } > db.findDocumentNonExistenceFieldDemo.insertOne({"StudentName":"David","StudentAge":26,"StudentMathMarks":78}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a5c809064dcd4a68b70e9") } Display all documents from a collection with the help of find() method. The query is as follows − > db.findDocumentNonExistenceFieldDemo.find().pretty(); The following is the output − { "_id" : ObjectId("5c8a5c629064dcd4a68b70e8"), "StudentName" : "John", "StudentAge" : 25 } { "_id" : ObjectId("5c8a5c809064dcd4a68b70e9"), "StudentName" : "David", "StudentAge" : 26, "StudentMathMarks" : 78 } Here is the query to find a document by the non-existence of a field − > db.findDocumentNonExistenceFieldDemo.find({ "StudentMathMarks" : { "$exists" : false } }).pretty();

The following is the output −

{
"_id" : ObjectId("5c8a5c629064dcd4a68b70e8"),
"StudentName" : "John",
"StudentAge" : 25
}
Published on 29-Mar-2019 10:05:14