MongoDB - findOne() Method

The findOne() method fetches a single matching document from a MongoDB collection, making it ideal when only one specific result is needed.

• Returns one matching document; the order is undefined unless a sort is specified.
• Returns null when no document matches the criteria.
• Supports projection to include or exclude specific fields.
• Reduces overhead when only one document is required.

Syntax

db.collection.findOne(query, projection)

• db.collection: Refers to the collection from which you want to retrieve the document.
• findOne(): The method used to retrieve a single document.
• query: A document that specifies the criteria to match the desired document.
• projection (optional): A document that specifies the fields to include or exclude in the returned document.

Examples of MongoDB findOne()

Here are a few practical examples using the student collection:

[
 { "_id": ObjectId("6011c71f781ba1a1c1ffc5b1"), "name": "Nicol", "language": "C++" },
 { "_id": ObjectId("6011c71f781ba1a1c1ffc5b2"), "name": "Alen", "language": "python" },
 { "_id": ObjectId("6011c71f781ba1a1c1ffc5b3"), "name": "Tim", "language": "python" }
]

Example 1: Empty Query

Retrieve a single document from the student collection.

Query:

db.student.findOne({})

Output:

{ "_id": ObjectId("6011c71f781ba1a1c1ffc5b1"), "name": "Nicol", "language": "C++" }

Example 2: Query Specification

Retrieve a document where the name is "Alen".

Query:

db.student.findOne({ name: "Alen" })

Output:

{ "_id": ObjectId("6011c71f781ba1a1c1ffc5b2"), "name": "Alen", "language": "python" }

Example 3: Include Specific Fields

Retrieve a document where the name is Tim and return only the name and language fields.

Query:

db.student.findOne({ name: "Tim" }, { _id: 0, name: 1, language: 1 })

Output:

{ "name": "Tim", "language": "python" }

Example 4: Exclude a Field

Retrieve a document where the name is "Nicol" and return all fields except the _id field.

Query:

db.student.findOne({ name: "Nicol" }, { _id: 0 })

Output:

{ "name": "Nicol", "language": "C++" }

Example 5: Matching Documents

Retrieve a document where the language is "python". If no document matches the criteria, findOne() returns null.

Query:

var result = db.student.findOne({ language: "python" });
print(result);

Output:

{ "_id": ObjectId("6011c71f781ba1a1c1ffc5b2"), "name": "Alen", "language": "python" }