# Check if value exists for a field in a MongoDB document?

MongoDBDatabaseBig Data Analytics

To check if value exists for a field in a MongoDB document, you can use find() along with $exists operator. Let us first create a collection with documents − > db.checkIfValueDemo.insertOne({"PlayerName":"John Smith","PlayerScores":[5000,98595858,554343]}); { "acknowledged" : true, "insertedId" : ObjectId("5cc6f507af8e7a4ca6b2ad98") } > db.checkIfValueDemo.insertOne({"PlayerName":"John Doe","PlayerScores":[]}); { "acknowledged" : true, "insertedId" : ObjectId("5cc6f512af8e7a4ca6b2ad99") } > db.checkIfValueDemo.insertOne({"PlayerName":"Carol Taylor","PlayerScores":[7848474,8746345353]}); { "acknowledged" : true, "insertedId" : ObjectId("5cc6f521af8e7a4ca6b2ad9a") } > db.checkIfValueDemo.insertOne({"PlayerName":"David Miller","PlayerScores":[]}); { "acknowledged" : true, "insertedId" : ObjectId("5cc6f531af8e7a4ca6b2ad9b") } Following is the query to display all documents from a collection with the help of find() method − > db.checkIfValueDemo.find().pretty(); This will produce the following output − { "_id" : ObjectId("5cc6f507af8e7a4ca6b2ad98"), "PlayerName" : "John Smith", "PlayerScores" : [ 5000, 98595858, 554343 ] } { "_id" : ObjectId("5cc6f512af8e7a4ca6b2ad99"), "PlayerName" : "John Doe", "PlayerScores" : [ ] } { "_id" : ObjectId("5cc6f521af8e7a4ca6b2ad9a"), "PlayerName" : "Carol Taylor", "PlayerScores" : [ 7848474, 8746345353 ] } { "_id" : ObjectId("5cc6f531af8e7a4ca6b2ad9b"), "PlayerName" : "David Miller", "PlayerScores" : [ ] } Following is the query to check if value exists for a field in a document. Here, we are checking for field 'PlayerScores with value [ ] − > db.checkIfValueDemo.find({'PlayerScores.0' : {$exists: true}}).count();

This will produce the following output

2
Published on 21-May-2019 08:56:27