$nin for not in set in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find documents where the field 'status' is not in the list ['A', 'D'].

MongoDB

db.collection.find({ status: { [1]: ['A', 'D'] } })

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

A$in

B$nin

C$eq

D$ne

Attempts:

3 left

💡 Hint

Common Mistakes

Using $in instead of $nin will select documents with values inside the list, not outside.

Using $ne only checks for not equal to a single value, not a list.

The $nin operator selects documents where the value of the field is not in the specified array.

2fill in blank

medium

Complete the code to find documents where 'category' is not in the array ['electronics', 'furniture'].

MongoDB

db.products.find({ category: { [1]: ['electronics', 'furniture'] } })

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

A$nin

B$eq

C$in

D$ne

Attempts:

3 left

💡 Hint

Common Mistakes

Using $in will include documents with those categories, not exclude them.

Using $ne only works for single values, not arrays.

The $nin operator filters out documents where 'category' matches any value in the given array.

3fill in blank

hard

Fix the error in the query to find documents where 'type' is not in ['admin', 'guest'].

MongoDB

db.users.find({ type: { [1]: ['admin', 'guest'] } })

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

A$nin

B$in

C$ne

D$not

Attempts:

3 left

💡 Hint

Common Mistakes

Using $in includes the values instead of excluding them.

Using $ne only excludes one value, not multiple.

The correct operator to exclude multiple values is $nin. Using $in or $ne will not exclude all listed values properly.

4fill in blank

hard

Fill both blanks to find documents where 'color' is not in ['red', 'blue'] and 'size' is not in ['small', 'medium'].

MongoDB

db.items.find({ color: { [1]: ['red', 'blue'] }, size: { [2]: ['small', 'medium'] } })

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

A$nin

B$in

C$ne

D$eq

Attempts:

3 left

💡 Hint

Common Mistakes

Using $in will include the values instead of excluding them.

Mixing $ne with $nin causes inconsistent filtering.

Both fields use $nin to exclude the listed values.

5fill in blank

hard

Fill all three blanks to find documents where 'status' is not in ['active', 'pending'], 'role' is not in ['admin', 'user'], and 'age' is not in [20, 30].

MongoDB

db.members.find({ status: { [1]: ['active', 'pending'] }, role: { [2]: ['admin', 'user'] }, age: { [3]: [20, 30] } })

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

A$in

B$nin

C$ne

D$eq

Attempts:

3 left

💡 Hint

Common Mistakes

Using $in includes the values instead of excluding them.

Using $ne only excludes single values, not lists.

All three fields use $nin to exclude the specified values.

Practice

1. What does the MongoDB operator $nin do in a query?

easy

A. Selects documents where the field's value is in the specified array

B. Selects documents where the field's value is NOT in the specified array

C. Updates documents with values in the specified array

D. Deletes documents where the field's value is in the specified array

Solution

1. Step 1: Understand the purpose of $nin

   The $nin operator is used to filter documents where a field's value is NOT included in a given list of values.

2. Step 2: Compare with other operators

   Unlike $in which selects values inside the array, $nin excludes those values.

3. Final Answer:

   Selects documents where the field's value is NOT in the specified array -> Option B

4. Quick Check:

   $nin excludes values = B [OK]

Hint: Remember: $nin means NOT in list [OK]

Common Mistakes:

• Confusing $nin with $in
• Thinking it updates or deletes documents
• Using it to select values inside the array

2. Which of the following is the correct syntax to find documents where the field status is NOT 'active' or 'pending' using $nin?

easy

A. { status: { $nin: ['active', 'pending'] } }

B. { status: { $nin: 'active', 'pending' } }

C. { status: { $nin: ['active'] || ['pending'] } }

D. { status: { $nin: 'active' && 'pending' } }

Solution

1. Step 1: Check the correct $nin syntax

   The $nin operator requires an array of values inside square brackets to specify the excluded set.

2. Step 2: Validate each option

   { status: { $nin: ['active', 'pending'] } } correctly uses an array with two strings. Options B, C, and D have syntax errors or invalid expressions.

3. Final Answer:

   { status: { $nin: ['active', 'pending'] } } -> Option A

4. Quick Check:

   Correct array syntax for $nin = A [OK]

Hint: Use square brackets for arrays in $nin [OK]

Common Mistakes:

• Using multiple arguments instead of an array
• Using logical operators inside $nin
• Missing square brackets around values

3. Given the collection products with documents:

{ name: 'Pen', category: 'stationery' }

{ name: 'Apple', category: 'fruit' }

{ name: 'Notebook', category: 'stationery' }

{ name: 'Carrot', category: 'vegetable' }

What will be the result of this query?

db.products.find({ category: { $nin: ['fruit', 'vegetable'] } })

medium

A. All documents returned

B. [{ name: 'Apple', category: 'fruit' }, { name: 'Carrot', category: 'vegetable' }]

C. [] (empty array)

D. [{ name: 'Pen', category: 'stationery' }, { name: 'Notebook', category: 'stationery' }]

Solution

1. Step 1: Understand the $nin filter

   The query excludes documents where category is 'fruit' or 'vegetable'.

2. Step 2: Identify matching documents

   Documents with category 'stationery' are not in ['fruit', 'vegetable'], so they match. 'Pen' and 'Notebook' have 'stationery'.

3. Final Answer:

   [{ name: 'Pen', category: 'stationery' }, { name: 'Notebook', category: 'stationery' }] -> Option D

4. Quick Check:

   Exclude 'fruit' and 'vegetable' = stationery items only [OK]

Hint: Exclude unwanted categories with $nin array [OK]

Common Mistakes:

• Confusing $nin with $in
• Expecting documents with excluded categories
• Assuming empty result when some match

4. You wrote this query to exclude users with roles 'admin' or 'moderator':

db.users.find({ role: { $nin: 'admin', 'moderator' } })

But it throws an error. What is the problem?

medium

A. The $nin operator requires an array, not multiple arguments

B. The field name role is misspelled

C. The query should use $in instead of $nin

D. MongoDB does not support $nin operator

Solution

1. Step 1: Check $nin syntax

   $nin expects a single array argument listing values to exclude.

2. Step 2: Identify the error in the query

   The query passes two separate string arguments instead of one array, causing syntax error.

3. Final Answer:

   The $nin operator requires an array, not multiple arguments -> Option A

4. Quick Check:

   $nin needs array input = C [OK]

Hint: Always wrap values in an array for $nin [OK]

Common Mistakes:

• Passing multiple arguments instead of an array
• Using wrong operator $in by mistake
• Assuming $nin is unsupported

5. You have a collection orders with documents:

{ orderId: 1, status: 'shipped' }

{ orderId: 2, status: 'pending' }

{ orderId: 3, status: 'cancelled' }

{ orderId: 4, status: 'delivered' }

You want to find orders NOT in statuses 'pending' or 'cancelled' AND exclude orders with orderId 4. Which query correctly uses $nin to achieve this?

hard

A. { status: { $nin: ['pending', 'cancelled'] }, orderId: { $ne: 4 } }

B. { status: { $nin: ['pending', 'cancelled', 4] } }

C. { status: { $nin: ['pending', 'cancelled'] }, orderId: { $nin: [4] } }

D. { status: { $nin: ['pending', 'cancelled'] }, orderId: { $in: [4] } }

Solution

1. Step 1: Exclude statuses 'pending' and 'cancelled'

   Use { status: { $nin: ['pending', 'cancelled'] } } to exclude these statuses.

2. Step 2: Exclude orderId 4 using $nin

   Use { orderId: { $nin: [4] } } to exclude orderId 4 as well.

3. Step 3: Combine conditions

   Both conditions together filter out unwanted statuses and orderId 4.

4. Final Answer:

   { status: { $nin: ['pending', 'cancelled'] }, orderId: { $nin: [4] } } -> Option C

5. Quick Check:

   Use $nin on both fields = A [OK]

Hint: Use separate $nin for each field to exclude multiple sets [OK]

Common Mistakes:

• Putting orderId inside status array
• Using $ne instead of $nin for multiple values
• Using $in to exclude values