Update elements inside an array in MongoDB?

To update elements inside an array, use $set in MongoDB. Let us create a collection with documents −

> db.demo494.insertOne( ... { ... ...    "CollegeDetails" : [ ...       { ...          "CollegeName" : "MIT", ...          "Fees" : 80000 ...       }, ...       { ...          "CollegeName" : "SU", ...          "Fees" : 90000 ...       } ...    ] ... } ... ) {    "acknowledged" : true,    "insertedId" : ObjectId("5e84a5c1b0f3fa88e22790c9") }

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

> db.demo494.find().pretty();

This will produce the following output −

{    "_id" : ObjectId("5e84a5c1b0f3fa88e22790c9"),    "CollegeDetails" : [       {          "CollegeName" : "MIT",          "Fees" : 80000       },       {          "CollegeName" : "SU",          "Fees" : 90000       }    ] }

Following is the query to update elements inside an array in MongoDB −

> db.demo494.update( ... ... { ...    "CollegeDetails.CollegeName": "MIT" ... }, ... ... { ...    $set: ...       { ...          "CollegeDetails.$.Fees" : 100000 ...       } ...    } ... ); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

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

> db.demo494.find().pretty();

This will produce the following output −

{    "_id" : ObjectId("5e84a5c1b0f3fa88e22790c9"),    "CollegeDetails" : [       {          "CollegeName" : "MIT",          "Fees" : 100000       },       {          "CollegeName" : "SU",          "Fees" : 90000       }    ] }