Update only a single MongoDB document without deleting any date

To update only a single document in MongoDB, use the updateOne() method. This method updates the first document that matches the specified filter criteria and preserves all existing data except for the fields being updated.

Syntax

db.collection.updateOne(
    { "field": "matchValue" },
    { $set: { "fieldToUpdate": "newValue" } }
);

Create Sample Data

Let us create a collection with documents ?

db.demo495.insertMany([
    {"FirstName":"Chris","Age":19},
    {"FirstName":"David","Age":21},
    {"FirstName":"Bob","Age":26},
    {"FirstName":"John","Age":22}
]);

{
   "acknowledged" : true,
   "insertedIds" : [
       ObjectId("5e84adfeb0f3fa88e22790ca"),
       ObjectId("5e84ae05b0f3fa88e22790cb"),
       ObjectId("5e84ae0eb0f3fa88e22790cc"),
       ObjectId("5e84ae15b0f3fa88e22790cd")
   ]
}

Display all documents from the collection ?

db.demo495.find();

{ "_id" : ObjectId("5e84adfeb0f3fa88e22790ca"), "FirstName" : "Chris", "Age" : 19 }
{ "_id" : ObjectId("5e84ae05b0f3fa88e22790cb"), "FirstName" : "David", "Age" : 21 }
{ "_id" : ObjectId("5e84ae0eb0f3fa88e22790cc"), "FirstName" : "Bob", "Age" : 26 }
{ "_id" : ObjectId("5e84ae15b0f3fa88e22790cd"), "FirstName" : "John", "Age" : 22 }

Example: Update Single Document

Update David's age from 21 to 23 ?

db.demo495.updateOne(
    {"FirstName":"David"},
    {$set: {"Age":23}}
);

{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }

Verify Result

Display all documents to verify the update ?

db.demo495.find();

{ "_id" : ObjectId("5e84adfeb0f3fa88e22790ca"), "FirstName" : "Chris", "Age" : 19 }
{ "_id" : ObjectId("5e84ae05b0f3fa88e22790cb"), "FirstName" : "David", "Age" : 23 }
{ "_id" : ObjectId("5e84ae0eb0f3fa88e22790cc"), "FirstName" : "Bob", "Age" : 26 }
{ "_id" : ObjectId("5e84ae15b0f3fa88e22790cd"), "FirstName" : "John", "Age" : 22 }

Key Points

• updateOne() updates only the first document that matches the filter
• Uses $set operator to modify specific fields without affecting other data
• Returns acknowledgment with matchedCount and modifiedCount

Conclusion

The updateOne() method safely updates a single document while preserving all existing fields. It's ideal when you need to modify specific data without affecting multiple documents or deleting any information.