limit method for pagination in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to limit the number of documents returned to 5.

MongoDB

db.collection.find().[1](5)

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

Acount

Bskip

Csort

Dlimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using skip() instead of limit() will skip documents rather than limit the count.

Using sort() changes order but not the number of documents.

Using count() returns a number, not documents.

The limit() method restricts the number of documents returned by the query. Here, it limits the result to 5 documents.

2fill in blank

medium

Complete the code to skip the first 10 documents and then limit the result to 5 documents.

MongoDB

db.collection.find().skip(10).[1](5)

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

Alimit

Bcount

Csort

Daggregate

Attempts:

3 left

💡 Hint

Common Mistakes

Using sort() here will reorder documents but not limit the count.

Using count() returns a number, not documents.

Using aggregate() is for complex pipelines, not simple pagination.

After skipping the first 10 documents, limit(5) returns the next 5 documents for pagination.

3fill in blank

hard

Fix the error in the code to correctly paginate by skipping 20 documents and limiting to 10.

MongoDB

db.collection.find().skip(20).[1](10)

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

Askip

Bcount

Climit

Dsort

Attempts:

3 left

💡 Hint

Common Mistakes

Placing limit() before skip() can cause unexpected results.

Using count() instead of limit() returns a number, not documents.

Using sort() does not limit the number of documents.

The limit() method should come after skip() to correctly paginate. The correct order is skip(20).limit(10).

4fill in blank

hard

Fill both blanks to skip the first 15 documents and limit the result to 7 documents.

MongoDB

db.collection.find().[1](15).[2](7)

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

Askip

Blimit

Csort

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the order of skip and limit.

Using sort() or count() instead of skip or limit.

Not using both methods together for pagination.

To paginate, first skip the documents you don't want, then limit how many you want to see.

5fill in blank

hard

Fill all three blanks to sort documents by 'date' descending, skip 30 documents, and limit to 10 documents.

MongoDB

db.collection.find().[1]({ date: -1 }).[2](30).[3](10)

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

Asort

Bskip

Climit

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using count() instead of limit() returns a number, not documents.

Changing the order of methods can cause wrong results.

Not sorting before skipping and limiting when order matters.

First, sort documents by date descending. Then skip 30 documents and limit the result to 10 for pagination.

Practice

1. What does the limit() method do in MongoDB queries?

easy

A. It updates documents in the collection.

B. It sorts the documents in ascending order.

C. It skips a specified number of documents.

D. It restricts the number of documents returned by the query.

Solution

1. Step 1: Understand the purpose of limit()

   The limit() method is used to control how many documents a query returns.

2. Step 2: Compare with other methods

   Unlike sort() which orders documents, or skip() which skips documents, limit() restricts the count of results.

3. Final Answer:

   It restricts the number of documents returned by the query. -> Option D

4. Quick Check:

   limit() controls result count = D [OK]

Hint: Limit sets max results returned, like page size [OK]

Common Mistakes:

• Confusing limit with skip
• Thinking limit sorts results
• Assuming limit updates data

2. Which of the following is the correct syntax to limit a MongoDB query to 5 documents?

easy

A. db.collection.find().limit(5)

B. db.collection.limit(5).find()

C. db.collection.find().skip(5)

D. db.collection.find(5).limit()

Solution

1. Step 1: Recall the correct method chaining

   In MongoDB, limit() is chained after find() to restrict results.

2. Step 2: Validate syntax correctness

   db.collection.find().limit(5) uses db.collection.find().limit(5), which is the correct syntax. Other options misuse method order or parameters.

3. Final Answer:

   db.collection.find().limit(5) -> Option A

4. Quick Check:

   Correct chaining is find() then limit() = A [OK]

Hint: Use find() first, then limit(n) to restrict results [OK]

Common Mistakes:

• Placing limit before find
• Using skip instead of limit
• Passing number inside find()

3. Given the collection products with documents: [{"name":"A"},{"name":"B"},{"name":"C"},{"name":"D"}], what will db.products.find().limit(2).toArray() return?

medium

A. [{"name":"A"},{"name":"B"},{"name":"C"}]

B. [{"name":"C"},{"name":"D"}]

C. [{"name":"A"},{"name":"B"}]

D. An error because limit cannot be used here

Solution

1. Step 1: Understand the default order of find()

   Without sorting, find() returns documents in insertion order: A, B, C, D.

2. Step 2: Apply limit(2) to restrict results

   Using limit(2) returns only the first two documents: A and B.

3. Final Answer:

   [{"name":"A"},{"name":"B"}] -> Option C

4. Quick Check:

   limit(2) returns first 2 docs = A [OK]

Hint: Limit returns first N documents in default order [OK]

Common Mistakes:

• Assuming limit returns last documents
• Expecting sorted results without sort()
• Thinking limit causes errors

4. What is wrong with this query for pagination?

db.users.find().limit(10).skip(5)

medium

A. The query is missing a sort() method for consistent pagination.

B. The order of limit and skip is incorrect; it causes a syntax error.

C. limit cannot be used with skip in the same query.

D. There is no error; the query is correct.

Solution

1. Step 1: Check method order validity

   In MongoDB, chaining limit() and skip() in any order is syntactically valid.

2. Step 2: Identify pagination best practice

   For consistent pagination, a sort() is needed to ensure stable document order across pages.

3. Final Answer:

   The query is missing a sort() method for consistent pagination. -> Option A

4. Quick Check:

   Pagination needs sort() for stable results = B [OK]

Hint: Always add sort() for reliable pagination [OK]

Common Mistakes:

• Thinking the order causes a syntax error
• Believing limit and skip can't be combined
• Ignoring the need for sort()

5. You want to show page 3 of a product list with 4 items per page, sorted by price ascending. Which query correctly uses limit() and skip() for this pagination?

hard

A. db.products.find().skip(4).limit(3).sort({price:1})

B. db.products.find().sort({price:1}).skip(8).limit(4)

C. db.products.find().limit(4).skip(8).sort({price:1})

D. db.products.find().sort({price:1}).limit(3).skip(4)

Solution

1. Step 1: Calculate skip value for page 3

   Each page has 4 items, so page 3 skips 2 pages: 2 * 4 = 8 documents to skip.

2. Step 2: Apply sort, skip, and limit in correct order

   Sort by price ascending first, then skip 8 documents, then limit to 4 documents for the page size.

3. Final Answer:

   db.products.find().sort({price:1}).skip(8).limit(4) -> Option B

4. Quick Check:

   Page 3 skip=8, limit=4, sorted = C [OK]

Hint: Skip (page-1)*size, then limit size after sort [OK]

Common Mistakes:

• Mixing skip and limit order
• Wrong skip calculation for page
• Missing sort for consistent order