MongoDB query to check the existence of multiple fields

To check the existence of multiple fields, use $exists along with $and. Let us create a collection with documents −

> db.demo475.insertOne({"StudentFirstName":"Chris","StudentAge":23});{    "acknowledged" : true,    "insertedId" : ObjectId("5e80c113b0f3fa88e2279088") } > db.demo475.insertOne({"StudentFirstName":"Bob","StudentAge":21,"StudentCountryName":"US"});{    "acknowledged" : true,    "insertedId" : ObjectId("5e80c127b0f3fa88e2279089") } > db.demo475.insertOne({"StudentFirstName":"David","StudentAge":22});{    "acknowledged" : true,    "insertedId" : ObjectId("5e80c135b0f3fa88e227908a") }

Display all documents from a collection with the help of find() method −

> db.demo475.find();

This will produce the following output −

{ "_id" : ObjectId("5e80c113b0f3fa88e2279088"), "StudentFirstName" : "Chris", "StudentAge" : 23 } { "_id" : ObjectId("5e80c127b0f3fa88e2279089"), "StudentFirstName" : "Bob", "StudentAge" : 21, "StudentCountryName" : "US" } { "_id" : ObjectId("5e80c135b0f3fa88e227908a"), "StudentFirstName" : "David", "StudentAge" : 22 }

Following is the query to check existence of multiple fields −

> db.demo475.find( ... { '$and': ...    [ { 'StudentFirstName': { '$exists': true } }, ...       { 'StudentAge': { '$exists': true } }, ...       { 'StudentCountryName': { '$exists': true } } ] ...    } ... );

This will produce the following output −

{ "_id" : ObjectId("5e80c127b0f3fa88e2279089"), "StudentFirstName" : "Bob", "StudentAge" : 21, "StudentCountryName" : "US" }