Introduction To GraphQL

What is GraphQL?

GraphQL is an API query language and runtime for fulfilling operations such as queries.

GraphQL uses a type system to define the data available in the API, including what entities and attributes (known as types and fields in GraphQL) exist and how types are connected (the data graph).

type Course {
  title: String
  author: String
  credits: Int
}

GraphQL operations (queries, mutations, or subscriptions) specify an entry-point and the expected data.

{
  Course {
    title
    author
  }
}

The response to a GraphQL operation will return the data requested.

{
  "data": {
    "Course": [
      {
        "title": "Introduction to Neo4J & GraphQL",
        "author": "neo4j"
      }
    ]
  }
}

Graphs, GraphQL and Neo4j

Graphs provide a natural way to represent data, where Nodes (or vertices) that represent entities that can be connected by Relationships (or edges).

GraphQL itself is a database-agnostic query language. Many database providers offer libraries that convert a GraphQL operation into a query language that works with the underlying data store e.g. SQL for relational databases and Cypher for graph databases.

Depending on the underlying data store and the data itself, the GraphQL library may need to undertake significant transformation and relationship mapping to access and make sense of the data, leading to the creation of unnatural tables with strange names are created, duplicated data to improve query response times and resulting in technical debt.

This is where Neo4j comes in. Neo4j is a native graph database that stores data in a graph structure. Neo4j is a natural fit for GraphQL as the GraphQL type system can map directly to the data graph.

The Neo4j Graph Platform is a complete solution for building graph applications and includes:

type Course {
  title: String
  author: String
  credits: Int
  lessons: [Lesson]
}

type Lesson {
  title: String
  content: String
  optional: Boolean
}

{
  Course(title: "Introduction to Neo4J & GraphQL") {
    title
    author
  }
}

Course(title: "Introduction to Neo4J & GraphQL")

{
  Course(title: "Introduction to Neo4J & GraphQL") {
    title
    lessons {
      title
      content
    }
  }
}

{
  Course(title: "Introduction to Neo4J & GraphQL") {
    title
    author
    credits
    lessons {
      title
      content
    }
  }
}

{
  "data": {
    "Course": [
      {
        "title": "Introduction to Neo4J & GraphQL",
        "author": "neo4j",
        "credits": 25,
        "lessons": [
          {
            "title": "Introduction To GraphQL",
            "content": "GraphQL is an API query language ..."
          }
        ]
      }
    ]
  }
}

const resolvers = {
  Query: {
    Course: (object, params, context, info) => {
      return context.db.coursesBySearch(params.searchString)
    }
  },
  Course: {
    lesson: (object, params, context, info) => {
      return context.db.lessonForCourse(object.courseId)
    }
  }
}