Queries and mutations in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a query in NestJS GraphQL?

A query is a way to ask the server for data without changing anything. It fetches information and returns it to you.

beginner

What is a mutation in NestJS GraphQL?

A mutation is a request to change data on the server, like adding, updating, or deleting something.

intermediate

How do you define a query method in a NestJS resolver?

Use the @Query() decorator above a method inside a resolver class. This method returns the data requested.

intermediate

How do you define a mutation method in a NestJS resolver?

Use the @Mutation() decorator above a method inside a resolver class. This method performs data changes and returns the result.

beginner

Why should queries not change data and mutations should?

Queries are for reading data only to keep things safe and predictable. Mutations change data because they represent actions that modify the server state.

Which decorator is used to define a query in a NestJS GraphQL resolver?

A @Resolver()

B @Query()

C @Mutation()

D @Controller()

The @Query() decorator marks a method as a GraphQL query resolver.

What does a mutation do in NestJS GraphQL?

A Changes data on the server

B Fetches data without changes

C Defines a new GraphQL type

D Handles HTTP requests

Mutations are used to change data on the server, like creating or updating records.

Where do you place the @Mutation() decorator in NestJS?

A Above a service method

B Above a controller method

C Above a resolver method

D Above a module class

The @Mutation() decorator is used above methods inside a resolver class.

Which of these is true about queries?

A They fetch data without side effects

B They modify data

C They are only used in REST APIs

D They require authentication always

Queries fetch data and should not cause side effects or data changes.

In NestJS GraphQL, what is the purpose of a resolver?

A To style the UI components

B To handle HTTP requests

C To store data in the database

D To define how queries and mutations fetch or change data

Resolvers define how GraphQL queries and mutations get or modify data.

Explain how queries and mutations differ in NestJS GraphQL and how you define them in a resolver.

Think about reading vs changing data and the decorators used.

Describe why it is important to separate queries and mutations in GraphQL and how this helps in building APIs with NestJS.

Consider safety, clarity, and API design benefits.