String and number types in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a document with a string field named 'name'.

MongoDB

db.users.insertOne({ name: [1] })

Drag options to blanks, or click blank then click option'

A"Alice"

B123

Ctrue

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number without quotes for a string field.

Using boolean or null instead of a string.

The 'name' field should be a string, so it must be enclosed in quotes.

2fill in blank

medium

Complete the code to find documents where the 'age' field is a number equal to 30.

MongoDB

db.users.find({ age: [1] })

Drag options to blanks, or click blank then click option'

A30

Btrue

Cnull

D"30"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string "30" instead of number 30.

Using boolean or null values.

The 'age' field is a number, so the value should be a number without quotes.

3fill in blank

hard

Fix the error in the query to find users with a string 'status' equal to 'active'.

MongoDB

db.users.find({ status: [1] })

Drag options to blanks, or click blank then click option'

Atrue

Bnull

C"active"

Dactive

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving out quotes around string values.

Using boolean or null instead of string.

String values must be enclosed in quotes in MongoDB queries.

4fill in blank

hard

Fill both blanks to create a document with a string 'title' and a number 'pages'.

MongoDB

db.books.insertOne({ title: [1], pages: [2] })

Drag options to blanks, or click blank then click option'

A"MongoDB Guide"

Btrue

C250

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the string value for title.

Quoting the number value for pages.

The 'title' is a string and must be quoted. The 'pages' is a number and should not be quoted.

5fill in blank

hard

Fill all three blanks to find documents where 'author' is a string, 'year' is a number greater than 2000, and 'available' is a boolean true.

MongoDB

db.books.find({ author: [1], year: { $gt: [2] }, available: [3] })

Drag options to blanks, or click blank then click option'

A"John Doe"

B2000

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the string author.

Quoting the number year.

Using false instead of true for available.

The 'author' is a string and needs quotes. The 'year' is a number and should be without quotes. The 'available' is a boolean true.

Practice

1. Which of the following is the correct way to store a string value in a MongoDB document?

easy

A. Use single quotes only, like 'Hello'

B. Write the text without quotes, like Hello

C. Write the text as a number, like 123

D. Use quotes around the text, like "Hello"

Solution

1. Step 1: Understand string representation in MongoDB

   Strings must be enclosed in quotes to be recognized as text.

2. Step 2: Identify correct syntax for strings

   Double quotes or single quotes can be used, but quotes are necessary around text.

3. Final Answer:

   Use quotes around the text, like "Hello" -> Option D

4. Quick Check:

   Strings need quotes = C [OK]

Hint: Strings always need quotes around text in MongoDB [OK]

Common Mistakes:

• Writing text without quotes causes errors
• Confusing numbers with strings
• Using numbers when text is needed

2. Which of the following is the correct way to store the number 42 in a MongoDB document?

easy

A. Write it as '42' with single quotes

B. Write it as "42" with quotes

C. Write it as 42 without quotes

D. Write it as forty-two without quotes

Solution

1. Step 1: Understand number representation in MongoDB

   Numbers are stored without quotes to be recognized as numeric values.

2. Step 2: Identify correct syntax for numbers

   Writing numbers without quotes stores them as numeric types, not strings.

3. Final Answer:

   Write it as 42 without quotes -> Option C

4. Quick Check:

   Numbers have no quotes = A [OK]

Hint: Numbers never have quotes in MongoDB documents [OK]

Common Mistakes:

• Putting numbers inside quotes makes them strings
• Using words instead of digits for numbers
• Mixing string and number types

3. What will be the output of this MongoDB query?

db.products.find({ price: 100 })

Assuming the collection has documents:

{ "name": "Pen", "price": 100 }
{ "name": "Book", "price": "100" }

medium

A. Returns only the document where price is number 100

B. Returns both documents because price matches 100

C. Returns only the document where price is string "100"

D. Returns no documents because of type mismatch

Solution

1. Step 1: Understand MongoDB type matching in queries

   MongoDB matches both value and type when querying, so number 100 matches only number 100.

2. Step 2: Analyze the documents

   Document with price as number 100 matches; document with price as string "100" does not.

3. Final Answer:

   Returns only the document where price is number 100 -> Option A

4. Quick Check:

   Query matches value and type = B [OK]

Hint: MongoDB matches type and value in queries [OK]

Common Mistakes:

• Assuming string and number values match
• Ignoring type differences in queries
• Expecting all similar values to match

4. You wrote this MongoDB insert command:

db.users.insertOne({ "age": "30" })

But you want age stored as a number. What is wrong?

medium

A. The insertOne command syntax is incorrect

B. Age is stored as a string because of quotes around 30

C. The field name should be "Age" with capital A

D. Age is stored as a number but should be a string

Solution

1. Step 1: Check the value type in the insert command

   Quotes around 30 make it a string, not a number.

2. Step 2: Understand how to store numbers

   To store as number, write 30 without quotes.

3. Final Answer:

   Age is stored as a string because of quotes around 30 -> Option B

4. Quick Check:

   Quotes make value string = D [OK]

Hint: Remove quotes to store numbers, add quotes for strings [OK]

Common Mistakes:

• Thinking quotes don't affect type
• Changing field name unnecessarily
• Assuming syntax error without checking value type

5. You have a collection with documents:

{ "item": "apple", "quantity": "10" }
{ "item": "banana", "quantity": 10 }

You want to find all documents where quantity is greater than 5. Which query works correctly?

hard

A. db.collection.find({ quantity: { $gt: NumberInt(5) } })

B. db.collection.find({ quantity: { $gt: "5" } })

C. db.collection.find({ quantity: { $gt: 5 } })

D. db.collection.find({ quantity: { $gt: 5 } }).toArray()

Solution

1. Step 1: Understand type comparison in MongoDB queries

   MongoDB compares values and types; string "10" is not greater than number 5.

2. Step 2: Use NumberInt to ensure numeric comparison

   Using NumberInt(5) ensures the query compares numbers, matching numeric quantity fields.

3. Final Answer:

   db.collection.find({ quantity: { $gt: NumberInt(5) } }) -> Option A

4. Quick Check:

   Use numeric type for numeric comparison = A [OK]

Hint: Use numeric types in queries to compare numbers correctly [OK]

Common Mistakes:

• Comparing strings with numbers directly
• Using quotes around numbers in queries
• Assuming all quantity fields are same type