MongoDB CRUD Operations: Insert and Find Documents

MongoDB is a NoSQL database that allows for flexible and scalable data storage using a document-based model. CRUD (Create, Read, Update, Delete) operations form the backbone of any database interaction and in MongoDB, these operations are performed on documents within collections.

In this article, we’ll learn two key CRUD operations such as Insert and Find. We’ll explore how to add new documents to a MongoDB collection and retrieve them efficiently.

Inserting Documents in MongoDB

To add data to MongoDB, we use the Insert operation. In MongoDB documents are stored in collections which are like tables in relational databases.

Documents are JSON-like structures consisting of key-value pairs, where we can insert data using the insertOne() or insertMany() methods.

1. Insert a Single Document Using insertOne()

The insertOne() method is used to insert a single document into a collection. The inserted document gets a unique _id field automatically if its not specified, which acts as the primary key.

Syntax:

db.collection.insertOne(document)

Example:

db.users.insertOne({
  "name": "Alice",
  "age": 30,
  "email": "[email protected]"
})

Output:

{
  "acknowledged": true,
  "insertedId": ObjectId("60d5f2a8c2957f489c4f4d23")
}

In this example, a new document is added to the users collection with the fields name, age, and email. MongoDB will generate an _id for the document if not provided.

2. Insert Multiple Documents Using insertMany()

The insertMany() method allows us to insert multiple documents at once. Each document is stored as a separate record in the collection and all documents receive their unique _id values.

Syntax:

db.collection.insertMany([document1, document2, ...])

Example:

db.users.insertMany([
  { "name": "Bob", "age": 25, "email": "[email protected]" },
  { "name": "Charlie", "age": 35, "email": "[email protected]" }
])

Output:

{
  "acknowledged": true,
  "insertedIds": [
    ObjectId("60d5f2b1c2957f489c4f4d24"),
    ObjectId("60d5f2b1c2957f489c4f4d25")
  ]
}

This command inserts two documents into the users collection. Each document is independent, with its own fields and values.

Finding Documents in MongoDB

After inserting documents, the next common operation is to retrieve them from the collection. MongoDB provides the find() method to search for documents based on specific criteria.

1. Find All Documents Using find()

The find() method without any parameters retrieves all documents from a collection. By default, MongoDB will return all fields for each document unless specified otherwise.

Syntax:

db.collection.find()

Example:

db.users.find()

Output:

[
  { "_id": ObjectId("60d5f2a8c2957f489c4f4d23"), "name": "Alice", "age": 30, "email": "[email protected]" },
  { "_id": ObjectId("60d5f2b1c2957f489c4f4d24"), "name": "Bob", "age": 25, "email": "[email protected]" },
  { "_id": ObjectId("60d5f2b1c2957f489c4f4d25"), "name": "Charlie", "age": 35, "email": "[email protected]" }
]

This query retrieves all documents from the users collection.

2. Find Documents Based on Criteria

To search for specific documents, you can pass a filter (query) object to the find() method. The query object specifies the criteria that documents must match.

Syntax:

db.collection.find(query)

Example:

db.users.find({ "age": { "$gt": 30 } })

Output:

[
  { "_id": ObjectId("60d5f2b1c2957f489c4f4d25"), "name": "Charlie", "age": 35, "email": "[email protected]" }
]

3. Find a Single Document: findOne()

The findOne() method is used to retrieve a single document that matches the query criteria. If multiple documents match, only the first one found is returned.

Example:

db.users.findOne({ "name": "Alice" })

Output:

{ "_id": ObjectId("60d5f2a8c2957f489c4f4d23"), "name": "Alice", "age": 30, "email": "[email protected]" }

Conclusion

In MongoDB, inserting and finding documents are fundamental operations for managing data. With insertOne() and insertMany(), you can add single or multiple documents to a collection. The find() method allows you to retrieve documents based on a range of criteria, making it a powerful tool for querying your data. By using projections, you can control which fields to return, further optimizing your queries.