Tables vs collections thinking in MongoDB - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find all documents in the 'users' collection.

MongoDB

db.users.[1]()

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

Afind

Bselect

CgetAll

Dquery

Attempts:

3 left

💡 Hint

Common Mistakes

Using SQL terms like 'select' instead of MongoDB methods.

Trying to use 'getAll' which is not a MongoDB method.

In MongoDB, find() is used to get all documents from a collection.

2fill in blank

medium

Complete the code to insert a new document into the 'products' collection.

MongoDB

db.products.[1]({ name: 'Book', price: 9.99 })

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

Acreate

Badd

CinsertOne

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'add' which is not a MongoDB method.

Trying to use 'create' which is not the correct MongoDB method.

insertOne() adds a single document to a MongoDB collection.

3fill in blank

hard

Fix the error in the code to update the price of a product named 'Pen' to 1.5.

MongoDB

db.products.updateOne({ name: 'Pen' }, { [1]: { price: 1.5 } })

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

Aupdate

B$set

Cset

D$update

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the dollar sign in the update operator.

Using 'update' instead of '$set'.

MongoDB uses $set to update specific fields in a document.

4fill in blank

hard

Fill both blanks to delete all documents where the 'status' is 'inactive' in the 'accounts' collection.

MongoDB

db.accounts.[1]([2]: 'inactive')

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

AdeleteMany

Bremove

Cstatus

Dstate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'remove' which is deprecated in newer MongoDB versions.

Using the wrong field name like 'state' instead of 'status'.

deleteMany() removes all documents matching the filter. The field to filter is 'status'.

5fill in blank

hard

Fill all three blanks to find documents in 'orders' where 'quantity' is greater than 10 and sort by 'date' descending.

MongoDB

db.orders.find({ [1]: { [2]: 10 } }).sort({ [3]: -1 })

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

Aquantity

B$gt

Cdate

Damount

Attempts:

3 left

💡 Hint

Common Mistakes

Using '$gte' instead of '$gt' for strictly greater than.

Sorting by 'amount' instead of 'date'.

Use quantity as the field, $gt for 'greater than', and sort by date descending with -1.

Practice

1. Which of the following best describes a MongoDB collection compared to a SQL table?

easy

A. A collection cannot store nested data.

B. A collection stores flexible documents without fixed columns.

C. A collection is organized strictly in rows and columns.

D. A collection requires fixed columns and strict schema.

Solution

1. Step 1: Understand MongoDB collections

   MongoDB collections store documents that can have different fields and structures.

2. Step 2: Compare with SQL tables

   SQL tables require fixed columns and rows, unlike collections.

3. Final Answer:

   A collection stores flexible documents without fixed columns. -> Option B

4. Quick Check:

   Collections = flexible documents [OK]

Hint: Collections are flexible; tables have fixed columns [OK]

Common Mistakes:

• Thinking collections require fixed columns
• Assuming collections store data in rows and columns
• Believing collections cannot have nested data

2. Which of the following is the correct way to create a collection named users in MongoDB?

easy

A. CREATE TABLE users;

B. CREATE COLLECTION users;

C. db.createCollection('users');

D. db.users.create();

Solution

1. Step 1: Recall MongoDB syntax for creating collections

   MongoDB uses db.createCollection('name') to create collections.

2. Step 2: Check other options

   Options A, B, and D use invalid MongoDB syntax.

3. Final Answer:

   db.createCollection('users'); -> Option C

4. Quick Check:

   Use db.createCollection('name') to create collections [OK]

Hint: Use db.createCollection('name') in MongoDB [OK]

Common Mistakes:

• Using SQL CREATE TABLE syntax in MongoDB
• Trying to call create() on collection object
• Using CREATE COLLECTION which is invalid

3. Given a MongoDB collection products with documents like { name: 'Pen', price: 1.5 } and { name: 'Notebook', price: 3 }, what will db.products.find({ price: { $gt: 2 } }) return?

medium

A. All products with price greater than 2

B. All products with price less than 2

C. All products with price equal to 2

D. Syntax error

Solution

1. Step 1: Understand the query filter

   The filter { price: { $gt: 2 } } selects documents where price is greater than 2.

2. Step 2: Apply filter to example data

   Only the document with price 3 matches; price 1.5 does not.

3. Final Answer:

   All products with price greater than 2 -> Option A

4. Quick Check:

   $gt means greater than [OK]

Hint: Remember $gt means greater than in MongoDB queries [OK]

Common Mistakes:

• Confusing $gt with $lt
• Thinking it returns products with price less than 2
• Assuming syntax error due to $gt usage

4. You tried to insert a document into a MongoDB collection with db.orders.insert({id: 1, item: 'Book'}) but got a deprecation warning. What is the likely cause?

medium

A. The insert method is deprecated; use insertOne or insertMany instead.

B. MongoDB requires documents to have a field named _id, not id.

C. The collection name must be plural, so 'orders' is invalid.

D. Documents cannot have string values in MongoDB.

Solution

1. Step 1: Check MongoDB insert method usage

   The insert() method is deprecated in modern MongoDB versions.

2. Step 2: Use correct insertion methods

   Use insertOne() or insertMany() to insert documents.

3. Final Answer:

   The insert method is deprecated; use insertOne or insertMany instead. -> Option A

4. Quick Check:

   Use insertOne/insertMany, not insert() [OK]

Hint: Use insertOne or insertMany, not insert() [OK]

Common Mistakes:

• Thinking _id field is mandatory to insert
• Believing collection names must be plural
• Assuming string values are invalid in documents

5. You want to store user profiles where each user can have different sets of contact methods (email, phone, social media). Which is the best approach in MongoDB?

hard

A. Create separate tables for each contact method and join them.

B. Store all contact methods as a single string field.

C. Use a fixed schema collection with all possible contact fields, leaving some empty.

D. Use a single collection with flexible documents holding different contact fields.

Solution

1. Step 1: Consider MongoDB's flexible schema

   MongoDB collections allow documents to have different fields, perfect for varying contact methods.

2. Step 2: Compare with relational approach

   Relational tables require joins and fixed schemas, less flexible for this use case.

3. Final Answer:

   Use a single collection with flexible documents holding different contact fields. -> Option D

4. Quick Check:

   Flexible documents fit varying user data best [OK]

Hint: Flexible documents handle varied user data best [OK]

Common Mistakes:

• Trying to use fixed schema for varying data
• Using multiple tables and joins in MongoDB
• Storing complex data as a single string