How to check if a field in MongoDB is [] or {}?

To check if a field in MongoDB is [] or {}, you can use the following syntax −

db.yourCollectionName.find({
   "yourOuterFieldName": { "$gt": {} },
   "yourOuterFieldName.0": { "$exists": false }
});

Let us first create a collection with documents -

> db.checkFieldDemo.insert([
...   { _id: 1010, StudentDetails: {} },
...   { _id: 1011, StudentDetails: [ { StudentId: 1 } ] },
...   { _id: 1012, StudentDetails: [ {} ] },
...   { _id: 1013 },
...   { _id: 1014, StudentDetails: null},
...   { _id: 1015, StudentDetails: { StudentId: 1 } }
... ]);
BulkWriteResult({
   "writeErrors" : [ ],
   "writeConcernErrors" : [ ],
   "nInserted" : 6,
   "nUpserted" : 0,
   "nMatched" : 0,
   "nModified" : 0,
   "nRemoved" : 0,
   "upserted" : [ ]
})

Following is the query to display all documents from a collection with the help of find() method −

> db.checkFieldDemo.find().pretty();

This will produce the following output −

{ "_id" : 1010, "StudentDetails" : { } }
{ "_id" : 1011, "StudentDetails" : [ { "StudentId" : 1 } ] }
{ "_id" : 1012, "StudentDetails" : [ { } ] }
{ "_id" : 1013 }
{ "_id" : 1014, "StudentDetails" : null }
{ "_id" : 1015, "StudentDetails" : { "StudentId" : 1 } }

Following is the query to check if a field in MongoDB is [] or {} −

> db.checkFieldDemo.find({
...   "StudentDetails": { "$gt": {} },
...   "StudentDetails.0": { "$exists": false }
... });

This will produce the following output −

{ "_id" : 1015, "StudentDetails" : { "StudentId" : 1 } }

Nishtha Thakur

Published on 23-May-2019 08:14:29

• Related Questions & Answers
• How to check if field is a number in MongoDB?
• How to check if field is null or empty in MySQL?
• How to check if a text field is empty or not in swift?
• Check if a field contains a string in MongoDB?
• Check whether field exist in MongoDB or not?
• How can I check whether a field exists or not in MongoDB?
• Check if value exists for a field in a MongoDB document?
• How to check empty field in a MongoDB collection?
• Check whether a field is empty or null in MySQL?
• How to check if a matrix is invertible or not in R?
• Check if a list is not empty in MongoDB?
• How to apply a condition only if field exists in MongoDB?
• How to Check if a Number is Odd or Even using Python?
• How to check if a given word is a Python keyword or not?
• How to check if a file is readable, writable, or, executable in Java?