Unset an attribute from a single array element in MongoDB?

Use $unset operator to unset an attribute. Let us first create a collection with documents −

> db.unsetAnAttributeDemo.insertOne( ...    { ...       _id: 1, ...       "StudentDetails": [ ...          { ...             "StudentFirstName": "Ramit", ...             "StudentCountryName":"UK" ...          }, ...          { ...             "StudentFirstName": "Bob", ...             "StudentCountryName":"US" ...          }, ...          { ...             "StudentFirstName": "Carol", ...             "StudentCountryName":"AUS" ... ...          } ...       ] ...    } ... ); { "acknowledged" : true, "insertedId" : 1 }

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

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

This will produce the following output −

{    "_id" : 1,    "StudentDetails" : [       {          "StudentFirstName" : "Ramit",          "StudentCountryName" : "UK"       },       {          "StudentFirstName" : "Bob",          "StudentCountryName" : "US"       },       {          "StudentFirstName" : "Carol",          "StudentCountryName" : "AUS"       }    ] }

Following is the query to unset an attribute from a single array element. The attribute “StudentCountryName” with value “AUS” will unset −

> db.unsetAnAttributeDemo.update({"StudentDetails.StudentCountryName": "AUS"}, {$unset:    {"StudentDetails.$.StudentCountryName": 1}});    WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Let us display the document from the collection to check that attribute StudentCountryName with value “AUS” has been cleared or not −

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

This will produce the following output −

{    "_id" : 1,    "StudentDetails" : [       {          "StudentFirstName" : "Ramit",          "StudentCountryName" : "UK"       },       {          "StudentFirstName" : "Bob",          "StudentCountryName" : "US"       },       {          "StudentFirstName" : "Carol"       }    ] }