GraphQL Cheatsheet

# GraphQL is a query language for APIs
# Single endpoint, client specifies data shape

# REST:   GET /users/1/posts
# GraphQL:
{
  user(id: 1) {
    name
    posts {
      title
    }
  }
}

# Response: exactly the shape requested
{
  "data": {
    "user": {
      "name": "Alice",
      "posts": [{ "title": "Hello" }]
    }
  }
}

# Scalar types
Int  Float  String  Boolean  ID

# Object type
type User {
  id: ID!              # ! = non-null
  name: String!
  email: String!
  age: Int
  posts: [Post!]!       # non-null list of non-null
}

type Post {
  id: ID!
  title: String!
  author: User!
}

# Input type (for mutations)
input CreateUserInput {
  name: String!
  email: String!
}

# Enum
enum Role { ADMIN USER GUEST }

# Interface
interface Node { id: ID! }

# Union
union SearchResult = User | Post

# Basic query
query {
  users {
    id
    name
  }
}

# With arguments
query {
  user(id: "1") {
    name
    email
  }
}

# Aliases
query {
  alice: user(id: "1") { name }
  bob: user(id: "2") { name }
}

# Schema root
type Query {
  users: [User!]!
  user(id: ID!): User
  posts(limit: Int = 10): [Post!]!
}

# Mutate data
mutation {
  createUser(input: {
    name: "Alice"
    email: "alice@test.com"
  }) {
    id
    name
  }
}

# Schema definition
type Mutation {
  createUser(input: CreateUserInput!): User!
  updateUser(id: ID!, name: String): User!
  deleteUser(id: ID!): Boolean!
}

# Query with variables
query GetUser($id: ID!) {
  user(id: $id) {
    name
    email
  }
}

# Variables (JSON)
{
  "id": "1"
}

# Mutation with variables
mutation CreateUser($input: CreateUserInput!) {
  createUser(input: $input) {
    id name
  }
}
# Variables
{ "input": { "name": "Alice", "email": "a@b.com" } }

# Reusable field sets
fragment UserFields on User {
  id
  name
  email
}

query {
  user(id: "1") { ...UserFields }
  admin: user(id: "2") { ...UserFields }
}

# Inline fragment (for unions/interfaces)
query {
  search(q: "hello") {
    ... on User { name email }
    ... on Post { title body }
  }
}

# Real-time updates via WebSocket
subscription {
  messageAdded(channelId: "1") {
    id
    text
    user { name }
  }
}

# Schema
type Subscription {
  messageAdded(channelId: ID!): Message!
  userOnline: User!
}

# Built-in directives
query GetUser($withEmail: Boolean!) {
  user(id: "1") {
    name
    email @include(if: $withEmail)
    age @skip(if: true)
  }
}

# @deprecated
type User {
  name: String!
  fullName: String @deprecated(reason: "Use name")
}