Nested field queries in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a nested field query in GraphQL?

A nested field query in GraphQL is when you request fields inside other fields, allowing you to fetch related data in a single query, like asking for a book's title and also the author's name inside it.

beginner

How do you write a nested field query to get a user's name and their posts' titles?

You write a query like:<br>

{ user { name posts { title } } }

This asks for the user's name and inside that, the titles of their posts.

beginner

Why are nested field queries useful in GraphQL?

They let you get all related data you need in one request, reducing the number of calls to the server and making your app faster and simpler.

intermediate

What happens if you request a nested field that does not exist in the schema?

GraphQL returns an error saying the field is unknown, so you need to check the schema to request only valid nested fields.

intermediate

Can nested field queries include arguments? Give an example.

Yes, nested fields can have arguments. For example:<br>

{ user(id: "1") { name posts(limit: 3) { title } } }

This fetches user with id 1 and limits posts to 3 titles.

What does a nested field query in GraphQL allow you to do?

A Fetch related data inside other fields in one query

B Run multiple queries at the same time

C Update multiple fields in one mutation

D Create new fields in the schema

Nested field queries let you fetch related data inside other fields in a single query.

How would you get a book's title and its author's name in one GraphQL query?

A { book { title author { name } } }

B { book { title } } { author { name } }

C { book.title author.name }

D { book: title, author: name }

Option A correctly nests the author field inside the book field.

If you request a nested field that does not exist, what happens?

A GraphQL returns null for that field

B GraphQL ignores the field silently

C GraphQL returns an error

D GraphQL crashes the server

GraphQL returns an error for unknown fields to help you fix your query.

Can you add arguments to nested fields in GraphQL queries?

A Only in mutations, not queries

B No, arguments only work on top-level fields

C Only if the server supports it

D Yes, to filter or limit nested data

Arguments can be added to nested fields to control the data returned.

Which of these is a valid nested field query?

A { user(posts) { title } }

B { user { posts { title } } }

C { user: posts: title }

D { user.posts.title }

Option B uses correct GraphQL syntax for nested fields.

Explain what nested field queries are in GraphQL and why they are useful.

Think about how you ask for details inside other details in one request.

Write a simple GraphQL query to get a user's name and the titles of their posts.

Use curly braces to nest fields inside each other.