Retrieving a Single Document in MongoDB: The findOne() Method

Learn how to efficiently retrieve a single document from a MongoDB collection using the findOne() method. Explore the various query operators and techniques to filter and find specific documents based on their attributes. This guide will provide you with the necessary knowledge to effectively extract individual documents from your MongoDB databases.

MongoDB: Find Single Document from Collection using findOne()

In MongoDB, collections are like tables in RDBMS, and documents are like records in those tables. The findOne() method retrieves a single document from a collection based on specified criteria.

MongoDB provides two methods for finding documents:

• findOne() - Returns the first document that matches the specified criteria.
• find() - Returns a cursor to the documents that match the criteria.

Sample Data

First, insert some documents into the employees collection:

db.employees.insertMany([
    { _id: 1, firstName: "John", lastName: "King", email: "john.king@abc.com", salary: 5000 },
    { _id: 2, firstName: "Sachin", lastName: "T", email: "sachin.t@abc.com", salary: 8000 },
    { _id: 3, firstName: "James", lastName: "Bond", email: "jamesb@abc.com", salary: 7500 },
    { _id: 4, firstName: "Steve", lastName: "J", email: "steve.j@abc.com", salary: 9000 },
    { _id: 5, firstName: "Kapil", lastName: "D", email: "kapil.d@abc.com", salary: 4500 },
    { _id: 6, firstName: "Amitabh", lastName: "B", email: "amitabh.b@abc.com", salary: 11000 }
])
        

Using findOne()

The findOne() method returns the first document that matches the specified criteria. If no criteria are provided, it returns the first document from the collection.

db.collection.findOne(query, projection)
        

Parameters:

• query: Optional. Criteria for finding the document.
• projection: Optional. Fields to include or exclude in the result.

Examples

1. Find the first document in the collection:

db.employees.findOne()
        

Output:

{
  _id: 1,
  firstName: 'John',
  lastName: 'King',
  email: 'john.king@abc.com',
  salary: 5000
}
    

2. Find a document with a specific firstName:

db.employees.findOne({ firstName: "Kapil" })
        

Output:

{
  _id: 5,
  firstName: 'Kapil',
  lastName: 'D',
  email: 'kapil.d@abc.com',
  salary: 4500
}
    

3. Find a document with a salary greater than 8000:

db.employees.findOne({ salary: { $gt: 8000 } })
        

Output:

{
  _id: 4,
  firstName: 'Steve',
  lastName: 'J',
  email: 'steve.j@abc.com',
  salary: 9000
}
    

4. Find a document with a specific firstName and project only certain fields:

db.employees.findOne({ firstName: "Sachin" }, { _id: 0, firstName: 1, lastName: 1 })
        

Output:

{ firstName: 'Sachin', lastName: 'T' }
    

Note: By default, the _id field is included in the results. To exclude it, specify { _id: 0 } in the projection.