MongoDB insertOne() Method

insertOne() adds a single document to a collection.

• Inserts one document at a time.
• Supports text, numbers, arrays, etc.
• Returns the inserted document’s unique _id.

Syntax:

db.collection_name.insertOne(<document>,{ writeConcern: <document>})

• collection_name: It refers to the name of the collection where the document will be inserted (the collection is created automatically if it does not exist).
• <document>: The document we want to insert. A document is a set of key-value pairs similar to a JSON object.
• writeConcern: If we need to specify a custom write concern (e.g., to ensure the data is written to multiple nodes), you can include this option.

Return Value of insertOne()

The insertOne() method returns the following:

• Acknowledgement: It returns acknowledged: true if the write concern was enabled.
• InsertedId: This field contains the _id value of the inserted document

Examples of MongoDB insertOne()

Here are few examples to understand how insertOne() works in MongoDB. In the following examples, we are working with:

• Database: gfg
• Collection: student
• Document: No document but, we want to insert in the form of the student name and student marks.

Example 1: Insert a Document without Specifying an _id Field

We are inserting the document whose name is Akshay and marks is 500 in the student collection. MongoDB will automatically assign a unique _id field to this document.

Query:

db.student.insertOne({Name: "Tim", Marks: 500})

Output:

MongoDB has inserted the document with a new ObjectId automatically generated for the _id field.

Example 2: Insert a Document Specifying an _id Field

We are inserting a document whose unique id is Stu102, name is Vishal, and marks is 230 in the student collection

Query:

db.student.insertOne({_id: "Stu102", Name: "Ron", Marks: 220})

Output:

We specified the _id as "Stu102", and MongoDB inserts the document successfully.

Example 3: Handling Write Concern with insertOne()

A custom write concern can be specified to ensure data is written to multiple nodes before being considered committed.

Query:

db.student.insertOne(
 { Name: "Maria", Marks: 420 },
 { writeConcern: { w: 1, j: true, wtimeout: 5000 } }
)

• w: Number of nodes that must confirm the write.
• j: Ensures data is written to disk (journaled).
• wtimeout: Maximum time to wait for confirmation.

Output:

Common Errors with insertOne()

While the insertOne() method is quite efficient, you might encounter some errors when:

• Duplicate _id: Existing _id values cause a DuplicateKeyError.
• Write concern errors: Unsatisfied write concerns result in a WriteConcernError.