Delete with filter conditions in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to delete all documents where the field "status" equals "inactive".

MongoDB

db.collection.deleteMany({"status": [1])

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

Ainactive

B"active"

C"inactive"

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string value.

Using the field name as the value.

The filter must match documents where the "status" field is the string "inactive". So the value must be a string in quotes.

2fill in blank

medium

Complete the code to delete a single document where the "username" is "guest".

MongoDB

db.collection.[1]({"username": "guest"})

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

AdeleteOne

Bremove

CdeleteMany

Ddrop

Attempts:

3 left

💡 Hint

Common Mistakes

Using deleteMany which deletes multiple documents.

Using drop which deletes the whole collection.

To delete a single document matching a filter, use deleteOne. deleteMany deletes all matching documents.

3fill in blank

hard

Fix the error in the code to delete documents where "age" is greater than 30.

MongoDB

db.collection.deleteMany({"age": [1] 30})

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

A$lt:

B$gt:

C>

D$gte:

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of $gt.

Omitting the colon after the operator.

MongoDB uses query operators like $gt for 'greater than'. It must be a key in an object, so the colon is needed.

4fill in blank

hard

Fill both blanks to delete documents where "score" is less than 50 and "passed" is false.

MongoDB

db.collection.deleteMany({"score": [1] 50, "passed": [2])

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

A$lt:

Bfalse

Ctrue

D$gt:

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of < for score.

Using string "false" instead of boolean false.

Use $lt for 'less than' and the boolean false for the "passed" field.

5fill in blank

hard

Fill all three blanks to delete documents where "category" is "electronics", "price" is greater than 100, and "inStock" is true.

MongoDB

db.collection.deleteMany({"category": [1], "price": [2] 100, "inStock": [3])

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

A"electronics"

B$gt:

Ctrue

D"clothing"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around "electronics".

Using > instead of $gt.

Using string "true" instead of boolean true.

The category is the string "electronics" (with quotes), the price filter uses $gt for 'greater than', and inStock is the boolean true.

Practice

1. What does the deleteMany method do in MongoDB when used with a filter condition?

easy

A. Deletes the entire collection regardless of the filter.

B. Deletes only the first document in the collection.

C. Deletes all documents that match the filter condition.

D. Updates documents instead of deleting them.

Solution

1. Step 1: Understand deleteMany purpose

   deleteMany is designed to remove multiple documents matching a filter.

2. Step 2: Apply filter condition effect

   Only documents matching the filter are deleted, not the entire collection.

3. Final Answer:

   Deletes all documents that match the filter condition. -> Option C

4. Quick Check:

   deleteMany removes all matching docs [OK]

Hint: Remember: deleteMany removes all matching documents [OK]

Common Mistakes:

• Confusing deleteMany with deleteOne
• Thinking deleteMany deletes entire collection
• Assuming deleteMany updates documents

2. Which of the following is the correct syntax to delete one document where the field status equals "inactive" in MongoDB?

easy

A. db.collection.deleteOne({status: "inactive"})

B. db.collection.delete({status: "inactive"})

C. db.collection.removeOne({status: "inactive"})

D. db.collection.deleteMany({status == "inactive"})

Solution

1. Step 1: Identify correct method for deleting one document

   The method to delete a single document is deleteOne.

2. Step 2: Check filter syntax correctness

   The filter uses a key-value pair with colon, not double equals or other syntax.

3. Final Answer:

   db.collection.deleteOne({status: "inactive"}) -> Option A

4. Quick Check:

   Correct method and filter syntax = db.collection.deleteOne({status: "inactive"}) [OK]

Hint: Use deleteOne with colon syntax for filters [OK]

Common Mistakes:

• Using delete instead of deleteOne
• Using == instead of : in filter
• Using removeOne which does not exist

3. Given the collection users with documents:
{name: "Alice", age: 30}
{name: "Bob", age: 25}
{name: "Charlie", age: 30}
What will be the result after running db.users.deleteMany({age: 30})?

medium

A. Only Alice's document is deleted.

B. Both Alice's and Charlie's documents are deleted.

C. Only Bob's document is deleted.

D. No documents are deleted.

Solution

1. Step 1: Identify filter condition effect

   The filter {age: 30} matches documents where age is exactly 30.

2. Step 2: Determine matching documents

   Alice and Charlie both have age 30, so both match and will be deleted by deleteMany.

3. Final Answer:

   Both Alice's and Charlie's documents are deleted. -> Option B

4. Quick Check:

   deleteMany removes all matching docs = Both Alice's and Charlie's documents are deleted. [OK]

Hint: deleteMany removes all docs matching filter, not just one [OK]

Common Mistakes:

• Deleting only one document with deleteMany
• Deleting documents not matching filter
• Confusing age 25 with 30

4. You run the command db.orders.deleteOne({orderId: 12345}) but no documents are deleted. What could be the problem?

medium

A. MongoDB does not support deleteOne method.

B. deleteOne deletes all documents, so it should have deleted more.

C. You must use deleteMany to delete any documents.

D. The filter field name or value might be incorrect or missing in documents.

Solution

1. Step 1: Understand deleteOne behavior

   deleteOne deletes only one document matching the filter if it exists.

2. Step 2: Check filter correctness

   If no document matches {orderId: 12345}, nothing is deleted. The field or value may be wrong or missing.

3. Final Answer:

   The filter field name or value might be incorrect or missing in documents. -> Option D

4. Quick Check:

   No matching document means no deletion [OK]

Hint: Check filter matches existing documents before deleting [OK]

Common Mistakes:

• Assuming deleteOne deletes all documents
• Using deleteMany when deleteOne is intended
• Thinking deleteOne does not exist

5. You want to delete all documents from the products collection where the stock field is less than or equal to 0. Which MongoDB command correctly achieves this?

hard

A. db.products.deleteMany({stock: {$lte: 0}})

B. db.products.deleteOne({stock <= 0})

C. db.products.remove({stock: {$lt: 0}})

D. db.products.deleteMany({stock: {$gte: 0}})

Solution

1. Step 1: Identify correct operator for less than or equal

   The MongoDB operator for less than or equal is $lte.

2. Step 2: Choose correct method and filter syntax

   deleteMany deletes all matching documents; filter must use {stock: {$lte: 0}}.

3. Final Answer:

   db.products.deleteMany({stock: {$lte: 0}}) -> Option A

4. Quick Check:

   Use $lte with deleteMany for all matching docs [OK]

Hint: Use $lte operator inside deleteMany filter for <= condition [OK]

Common Mistakes:

• Using incorrect comparison syntax like stock <= 0
• Using deleteOne instead of deleteMany for multiple docs
• Using $gte instead of $lte