Replace an array field value with MongoDB?

You can use positional operator $. Let us first create a collection with documents −

> db.replaceAnArrayFieldValueDemo.insertOne({"StudentTechnicalSubjects":["MySQL","SQL Server","PL/SQL"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cea41e0ef71edecf6a1f68f")
}

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

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

This will produce the following output −

{
   "_id" : ObjectId("5cea41e0ef71edecf6a1f68f"),
   "StudentTechnicalSubjects" : [
      "MySQL",
      "SQL Server",
      "PL/SQL"
   ]
}

Following is the query to replace an array field value. Here, we are updating “SQL Server” with “MongoDB” −

> db.replaceAnArrayFieldValueDemo.update(
   {"StudentTechnicalSubjects":"SQL Server"},
   { $set: { 'StudentTechnicalSubjects.$': "MongoDB" }}
);
WriteResult({ "nMatched" : 0, "nUpserted" : 0, "nModified" : 0 })

Let us check the document once again −

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

This will produce the following output −

{
   "_id" : ObjectId("5cea41e0ef71edecf6a1f68f"),
   "StudentTechnicalSubjects" : [
      "MySQL",
      "MongoDB",
      "PL/SQL"
   ]
}