One-to-many relationships in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a one-to-many relationship in databases?

It is a connection where one record in a table can be linked to many records in another table. For example, one author can write many books.

beginner

How do you represent a one-to-many relationship in GraphQL?

You use a field in the 'one' type that returns a list of the 'many' type. For example, an Author type has a books field that returns a list of Book types.

intermediate

Why is a foreign key important in one-to-many relationships?

A foreign key in the 'many' table points back to the 'one' table, linking records together. It helps keep data connected and organized.

intermediate

Example: In GraphQL, how would you define an Author type with many books?

type Author { id: ID! name: String! books: [Book!]! } This means each author has a list of books.

beginner

What happens if you try to query a one-to-many field in GraphQL?

You get a list of related records. For example, querying an author's books returns all books written by that author.

In a one-to-many relationship, which side holds the foreign key?

A The 'many' side

B The 'one' side

C Both sides

D Neither side

The 'many' side holds the foreign key pointing to the 'one' side.

How do you represent multiple related items in a GraphQL type?

A As a single object

B As a list of objects

C As a scalar value

D As a string

You use a list (array) of objects to represent multiple related items.

Which GraphQL type field best shows a one-to-many relationship?

A books: [Book!]

B books: Book

C books: String

D books: ID

A list of Book objects (books: [Book!]) shows many books related to one author.

What does the exclamation mark (!) mean in GraphQL types like ID! or [Book!]?

A The field is optional

B The field is deprecated

C The field is required (non-null)

D The field is a list

The exclamation mark means the field cannot be null; it is required.

If an Author has many Books, what would a query for an author’s books return?

A A single book

B An error

C Nothing

D A list of books

The query returns a list of all books related to that author.

Explain how a one-to-many relationship works using a real-life example.

Think about how one teacher can have many students.

Describe how you would define a one-to-many relationship in a GraphQL schema.

Focus on how the 'one' type includes a list of the 'many' type.