MongoDB Data Types

MongoDB Data Types

In MongoDB, documents are stored in a format called BSON (Binary JSON). BSON supports a rich set of data types that allow you to store and query your data efficiently.

Let’s explore the most commonly used MongoDB data types with examples.

String

Strings are used to store text data. They must be enclosed in double quotes.

    db.users.insertOne({
      name: "Alice"
    });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("...")
    }
    

Q: Can we use single quotes for string values in MongoDB?

A: No. MongoDB strictly uses double quotes for keys and string values in BSON/JSON format.

Number (Int, Double)

MongoDB supports integers and floating-point numbers.

    db.products.insertOne({
      name: "Mouse",
      price: 499,             // integer
      rating: 4.5             // floating point
    });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("...")
    }
    

Note: MongoDB automatically identifies whether the number is an integer or double based on the value.

Boolean

Booleans store true/false values, commonly used for flags and status indicators.

    db.settings.insertOne({
      darkMode: true,
      notifications: false
    });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("...")
    }
    

Array

Arrays can hold multiple values, including mixed types or nested documents.

    db.users.insertOne({
      name: "Bob",
      hobbies: ["reading", "gaming", "cycling"]
    });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("...")
    }
    

Q: Can arrays in MongoDB store different data types?

A: Yes, arrays can include strings, numbers, booleans, even other arrays or objects.

Object / Embedded Document

MongoDB allows you to store objects (documents within documents), also known as embedded documents.

    db.users.insertOne({
      name: "Charlie",
      address: {
        city: "Mumbai",
        zip: 400001
      }
    });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("...")
    }
    

Q: Why use embedded documents?

A: They allow related data to be stored together, improving query performance and reducing joins.

ObjectId

ObjectId is the default unique identifier MongoDB assigns to each document. It is a 12-byte hexadecimal string.

    db.items.insertOne({ name: "Chair" });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("66321faabc1234567890abcd")
    }
    

Q: Can I assign my own _id instead of ObjectId?

A: Yes. You can insert documents with custom _id values if needed:

    db.items.insertOne({ _id: "custom123", name: "Table" });
    

Date

Dates are stored using the ISODate() function and support date/time operations.

    db.logs.insertOne({
      event: "User Login",
      timestamp: new Date()
    });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("...")
    }
    

Q: How can I query documents created today?

A: You can use $gte with ISODate() to filter by time range.

Null

Represents a missing or null value.

    db.users.insertOne({
      name: "David",
      phone: null
    });
    

Output:

    {
      acknowledged: true,
      insertedId: ObjectId("...")
    }
    

Summary Table of Core Types

Type	Example	Description
String	"hello"	Text value
Number	42, 3.14	Integer or float
Boolean	true	Logical value
Array	[1, 2, 3]	List of values
Object	{ a: 1 }	Nested document
ObjectId	ObjectId("...")	Unique ID
Date	ISODate("...")	Timestamp
Null	null	Missing or empty

Conclusion

MongoDB provides a flexible set of data types that align naturally with most programming languages. From simple types like strings and numbers to advanced types like embedded objects and arrays, MongoDB makes it easy to model real-world data in a readable and scalable way.

In the next lesson, we’ll explore how to create databases and collections, and how these data types come together in real CRUD operations.