BSON data types overview in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is BSON in MongoDB?

BSON is a binary format used by MongoDB to store data. It is like JSON but includes extra data types and is faster for computers to read and write.

beginner

Name three common BSON data types.

Common BSON data types include String (text), Int32 (small whole numbers), and Date (date and time).

beginner

What BSON type would you use to store true or false values?

You use the Boolean BSON type to store true or false values.

intermediate

How does BSON handle binary data like images or files?

BSON uses the Binary data type to store binary data such as images or files inside the database.

intermediate

Why does BSON include special types like ObjectId and Date?

BSON includes special types like ObjectId to uniquely identify documents and Date to store time information efficiently, which JSON does not support natively.

Which BSON data type is used to store text?

A String

B Int32

C Boolean

D Binary

The String type stores text data in BSON.

What BSON type uniquely identifies a document in MongoDB?

A ObjectId

B Double

C Boolean

D Date

ObjectId is a special BSON type used as a unique ID for documents.

Which BSON type would you use to store a true or false value?

A String

B Boolean

C Int64

D Array

Boolean stores true or false values in BSON.

How does BSON store date and time information?

A As a String

B As an Int32

C Using the Date type

D Using Binary

BSON has a special Date type to store date and time efficiently.

Which BSON type is best for storing images or files?

A Boolean

B String

C ObjectId

D Binary

Binary type stores raw binary data like images or files.

List and describe at least five BSON data types and their uses.

Think about text, numbers, true/false, time, unique IDs, and files.

Explain why BSON is used in MongoDB instead of plain JSON.

Consider what JSON cannot do well that BSON can.

Practice

1. Which BSON data type is used to store a unique identifier for documents in MongoDB?

easy

A. Date

B. String

C. ObjectId

D. Boolean

Solution

1. Step 1: Understand the purpose of ObjectId

   ObjectId is a special BSON type designed to uniquely identify documents in MongoDB collections.

2. Step 2: Compare with other types

   String stores text, Boolean stores true/false, Date stores time values. None of these uniquely identify documents like ObjectId.

3. Final Answer:

   ObjectId -> Option C

4. Quick Check:

   BSON unique ID = ObjectId [OK]

Hint: Unique document IDs in MongoDB are ObjectIds [OK]

Common Mistakes:

• Confusing String with ObjectId for unique IDs
• Thinking Boolean can identify documents
• Assuming Date stores unique identifiers

2. Which of the following is the correct BSON data type to store a true or false value in MongoDB?

easy

A. Integer

B. Boolean

C. String

D. Array

Solution

1. Step 1: Identify the BSON type for true/false

   Boolean is the BSON data type used to store true or false values.

2. Step 2: Eliminate other types

   Integer stores numbers, String stores text, Array stores lists. None represent true/false directly.

3. Final Answer:

   Boolean -> Option B

4. Quick Check:

   True/false = Boolean [OK]

Hint: True or false values use Boolean type [OK]

Common Mistakes:

• Using Integer for true/false
• Confusing String with Boolean
• Choosing Array for single true/false

3. Given the following MongoDB document:
{ "name": "Alice", "age": 30, "member": true }
What BSON data types are used for the fields name, age, and member respectively?

medium

A. String, Boolean, Integer

B. String, String, Boolean

C. ObjectId, Integer, Boolean

D. String, Integer, Boolean

Solution

1. Step 1: Identify each field's value type

   "name" is text, so String; "age" is a number, so Integer; "member" is true/false, so Boolean.

2. Step 2: Match with options

   String, Integer, Boolean matches String, Integer, Boolean in order. Others mismatch types.

3. Final Answer:

   String, Integer, Boolean -> Option D

4. Quick Check:

   Text, number, true/false = String, Integer, Boolean [OK]

Hint: Match field values to String, Integer, Boolean types [OK]

Common Mistakes:

• Confusing Integer with String for numbers
• Mixing Boolean and Integer types
• Assuming ObjectId for name field

4. You try to insert this document into MongoDB:
{ "date": "2023-01-01" }
But you want the date field to be stored as a BSON Date type. What is the issue and how to fix it?

medium

A. The date is a string; convert it to BSON Date using ISODate()

B. The date is missing; add a date field

C. The date format is invalid; use YYYY/DD/MM instead

D. MongoDB does not support Date type; use String instead

Solution

1. Step 1: Identify the current data type of date field

   The date is stored as a string because it is enclosed in quotes.

2. Step 2: Convert string to BSON Date type

   Use MongoDB's ISODate() function to store the date as BSON Date type.

3. Final Answer:

   The date is a string; convert it to BSON Date using ISODate() -> Option A

4. Quick Check:

   Date string needs ISODate() for BSON Date [OK]

Hint: Use ISODate() to store dates, not strings [OK]

Common Mistakes:

• Assuming string is automatically Date
• Changing date format incorrectly
• Believing MongoDB lacks Date type

5. You want to store a list of tags for a blog post in MongoDB. Which BSON data type should you use to store multiple tag strings together?

hard

A. Array

B. ObjectId

C. Boolean

D. Date

Solution

1. Step 1: Understand the need to store multiple values

   A list of tags means multiple values grouped together.

2. Step 2: Identify BSON type for multiple values

   Array is the BSON type used to store lists or collections of values.

3. Final Answer:

   Array -> Option A

4. Quick Check:

   Multiple values = Array type [OK]

Hint: Use Array type for lists of values [OK]

Common Mistakes:

• Using ObjectId for lists
• Choosing Boolean for multiple tags
• Trying to store list as Date