MongoDB Data Types Explained with Examples

 

Understanding MongoDB data types is essential for designing efficient databases and writing correct queries. Unlike traditional SQL databases, MongoDB offers flexible and rich data types that work naturally with modern applications.

In this article, we’ll explore the most important MongoDB data types, explain when to use them, and show clear examples for beginners.

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Why MongoDB Data Types Matter

Choosing the right data type helps you:

• Store data efficiently

• Write accurate queries

• Improve performance

• Avoid unexpected bugs

MongoDB stores data in BSON (Binary JSON), which extends JSON with additional data types.

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1. String

The String type is used to store text data.

Example

{
  "name": "Rahul Gupta",
  "email": "rahul@example.com"
}

Use strings for:

• Names

• Emails

• Descriptions

• Labels

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2. Number (Integer, Long, Double, Decimal)

MongoDB supports multiple numeric types.

Integer (int)

{ "age": 28 }

Double

{ "rating": 4.5 }

Decimal128 (High Precision)

{ "price": NumberDecimal("999.99") }

👉 Use Decimal128 for money-related values to avoid rounding issues.

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3. Boolean

The Boolean type stores true or false.

Example

{ "isActive": true }

Common use cases:

• Status flags

• Feature toggles

• Verification states

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4. Date

The Date type stores date and time values.

Example

{
  "createdAt": new Date()
}

Dates are stored in UTC format internally.

Use dates for:

• Timestamps

• Logs

• Event tracking

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5. ObjectId

ObjectId is a special data type used for the _id field by default.

Example

"_id": ObjectId("65b2a9f2c1e4a123456789ab")

It is:

• Unique

• Time-based

• Indexed automatically

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6. Array

Arrays allow you to store multiple values in a single field.

Example

{
  "skills": ["MongoDB", "Node.js", "React"]
}

Arrays can contain:

• Strings

• Numbers

• Objects

• Even nested arrays

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7. Embedded Document (Object)

MongoDB supports nested objects.

Example

{
  "address": {
    "city": "Delhi",
    "pincode": "110001",
    "country": "India"
  }
}

Embedded documents reduce the need for joins and improve read performance.

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8. Null

The null type represents an empty or missing value.

Example

{
  "middleName": null
}

Useful when:

• Data is optional

• Value is unknown or not applicable

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9. Binary Data

Binary data stores non-text data like files.

Example

{
  "file": BinData(0, "U29tZUJpbmFyeURhdGE=")
}

Often used with GridFS for large files.

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10. Regular Expression

Used for pattern matching in strings.

Example

db.users.find({ name: { $regex: "^Ra", $options: "i" } });

This finds names starting with “Ra”, case-insensitive.

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11. Mixed Data Types in MongoDB

MongoDB allows different data types in the same field across documents.

Example

{ "score": 90 }

{ "score": "Ninety" }

⚠️ This flexibility is powerful but should be used carefully.

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12. Common MongoDB Data Types Summary

Data Type	Description
String	Text values
Number	Numeric values
Boolean	true / false
Date	Date and time
ObjectId	Unique document ID
Array	List of values
Object	Embedded document
Null	Empty value
Binary	File data
Regex	Pattern matching

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Best Practices for Using MongoDB Data Types

• Use ObjectId for references

• Use Date for timestamps

• Use Decimal128 for prices

• Avoid mixing data types in the same field

• Keep document structure consistent

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Final Thoughts

MongoDB’s rich set of data types gives developers incredible flexibility. When used correctly, they make your database more powerful, readable, and performant.

For beginners, understanding these data types is a big step toward mastering MongoDB.