Delete mutation pattern in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the result of this delete mutation?

Given the following GraphQL mutation to delete a user by ID, what will be the output if the user with ID 5 exists?

GraphQL

mutation {
  deleteUser(id: 5) {
    id
    name
  }
}

A { "errors": [ { "message": "User not found" } ] }

B { "data": { "deleteUser": null } }

C { "data": { "deleteUser": { "id": 5, "name": "Alice" } } }

D { "data": { "deleteUser": { "id": 6, "name": "Bob" } } }

💡 Hint

Think about what the mutation returns after deleting an existing user.

The delete mutation returns the deleted user's data if the user exists. Since user with ID 5 exists, it returns their id and name.

🧠 Conceptual

intermediate

Which statement about delete mutations is true?

Choose the correct statement about delete mutations in GraphQL.

A Delete mutations always return a boolean indicating success or failure.

B Delete mutations can return the deleted object's data for confirmation.

C Delete mutations cannot accept arguments to specify which record to delete.

D Delete mutations automatically cascade delete related records without configuration.

💡 Hint

Consider what information is useful to return after deleting an item.

Delete mutations often return the deleted object's data so clients can confirm what was deleted. They do not always return just a boolean.

📝 Syntax

advanced

Identify the syntax error in this delete mutation

Which option contains the correct syntax for deleting a post by ID?

GraphQL

mutation {
  deletePost(id: 10) {
    id
    title
  }
}

A

mutation {
  deletePost(id: 10) {
    id
    title
  }
}

B

mutation {
  deletePost(id: "10") {
    id
    title
  }
}

C

mutation {
  deletePost(postId: 10) {
    id
    title
  }
}

D

mutation {
  deletePost {
    id
    title
  }
}

💡 Hint

Check the argument name and type carefully.

Option A uses the correct argument name 'id' with an integer value. Option A uses a string instead of integer. Option A uses wrong argument name 'postId'. Option A omits the required argument.

❓ optimization

advanced

How to optimize a delete mutation for batch deletions?

You want to delete multiple users by their IDs in one mutation call. Which approach is best?

A Create a deleteUsers mutation that accepts a list of IDs and deletes them all.

B Call the deleteUser mutation multiple times, once per ID.

C Use a query to fetch users and then delete them one by one on the client side.

D Delete users by sending a comma-separated string of IDs to deleteUser mutation.

💡 Hint

Think about reducing network calls and improving efficiency.

Batch deleting with a mutation that accepts a list of IDs reduces network overhead and improves performance.

🔧 Debug

expert

Why does this delete mutation return null instead of deleted data?

Given this mutation:

mutation {
  deleteComment(id: 7) {
    id
    content
  }
}

The server returns { "data": { "deleteComment": null } }. What is the most likely reason?

A The client query is missing required fields in the selection set.

B The mutation resolver forgot to return the deleted comment data.

C The server has a syntax error in the deleteComment mutation definition.

D The comment with ID 7 does not exist in the database.

💡 Hint

Consider what happens if the item to delete is not found.

If the item to delete does not exist, the resolver often returns null to indicate nothing was deleted.