Create mutation pattern in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the result of this GraphQL mutation?

Given the following GraphQL mutation to create a new user, what will be the output if the mutation is successful?

GraphQL

mutation {
  createUser(input: {name: "Alice", email: "[e-mail]"}) {
    id
    name
    email
  }
}

A { "data": { "createUser": { "name": "Alice" } } }

B { "data": { "createUser": { "id": "1", "name": "Alice", "email": "[e-mail]" } } }

C { "errors": [ { "message": "Field 'createUser' not found" } ] }

D { "data": { "createUser": null } }

💡 Hint

Successful mutations return the created object with requested fields.

The mutation returns the newly created user object with all requested fields: id, name, and email.

📝 Syntax

intermediate

Identify the syntax error in this mutation

Which option correctly fixes the syntax error in this GraphQL mutation?

GraphQL

mutation {
  createUser(input: {name: "Bob", email: "[e-mail]") {
    id
    name
  }
}

A

mutation {
  createUser(input: {name: "Bob", email: "[e-mail]"} {
    id
    name
  }
}

B

mutation {
  createUser(input: {name: "Bob", email: [e-mail]}) {
    id
    name
  }
}

C

mutation {
  createUser(input: {name: "Bob", email: "[e-mail]"}) {
    id
    name
  }
}

D

mutation {
  createUser(input: name: "Bob", email: "[e-mail]") {
    id
    name
  }
}

💡 Hint

Check for balanced parentheses and correct object syntax.

Option C correctly closes the input object with a closing brace and parenthesis.

❓ optimization

advanced

Optimize this mutation to reduce response size

You want to create a new post but only need the post ID in the response. Which mutation query is optimized for this?

GraphQL

mutation {
  createPost(input: {title: "Hello", content: "World"}) {
    id
    title
    content
    createdAt
  }
}

A

mutation {
  createPost(input: {title: "Hello", content: "World"}) {
    id
  }
}

B

mutation {
  createPost(input: {title: "Hello", content: "World"}) {
    title
  }
}

C

mutation {
  createPost(input: {title: "Hello", content: "World"}) {
    id
    title
  }
}

D

mutation {
  createPost(input: {title: "Hello", content: "World"}) {
    id
    content
  }
}

💡 Hint

Request only the fields you need to reduce response size.

Option A requests only the post ID, minimizing data returned.

🔧 Debug

advanced

Why does this mutation return an error?

Given this mutation, why does it return an error?

GraphQL

mutation {
  createUser(input: {name: "Eve"}) {
    id
    name
    email
  }
}

A The mutation is missing a closing brace causing a syntax error.

B The mutation name createUser is invalid and does not exist in the schema.

C The requested fields id, name, and email are not selectable in the response.

D The email field is required in input but missing, causing a validation error.

💡 Hint

Check required input fields in the schema.

The input requires an email field which is missing, so the server returns a validation error.

🧠 Conceptual

expert

What is the purpose of the input type in GraphQL mutations?

Why do GraphQL mutations commonly use an input type object for arguments instead of separate scalar arguments?

A To group related fields into a single argument for better structure and future extensibility.

B To force clients to send all fields even if they are optional.

C To make the mutation syntax identical to queries.

D To prevent mutations from returning any data in the response.

💡 Hint

Think about how input objects help organize data.

Input types group related fields into one argument, making mutations easier to maintain and extend.