GraphQL is a query language for APIs with this client can define what they need and server get exactly that, nothing more and nothing less.

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GraphQL is a query language for web APIs and a runtime for fulfilling queries with existing data. GraphQL gives clients the power to ask for precisely what they need, making it easy to evolve APIs with powerful developer tools.

This course is an introduction to GraphQL using the Node.js JavaScript runtime environment and Apollo Server. You’ll start with an introduction to GraphQL’s architecture and functions before exploring the structure of GraphQL data and learning to perform meaningful, complex queries. You’ll then learn how to update server data using mutations. Next, you’ll explore the GraphQL type system and schemas to set up a GraphQL server using Apollo Server. Once the server is set up, you’ll implement a full GraphQL application using Apollo and Node.js.

By the end of this course, you’ll have a rich understanding of GraphQL’s architecture and methodology and be prepared to deploy GraphQL applications to the web using Apollo and Node.js.

Getting Started with GraphQL using Node.js

GraphQL fragments can refer to themselves.


A field may or may not exist for the given type.


Which statement about GraphQL validationis correct?


Which statement about GraphQL validationis correct?

What's the potential root cause of the GraphQL query error response below?

```
{
  "errors": [
    {
      "message": "Field \"pizza\" must not have a selection since type \"String!\" has no subfields.",
      // more error details
    }
  ]
}
```

What’s the potential root cause of the GraphQL query error response below?
<pre><code>{
 &quot;errors&quot;: [
 {
 &quot;message&quot;: &quot;Field \&quot;pizza\&quot; must not have a selection since type \&quot;String!\&quot; has no subfields.&quot;,
 // more error details
 }
 ]
}
</code></pre>

```
{
  "errors": [
    {
      "message": "Maximum call stack size exceeded",
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
         // Stack trace
      }
    }
  ]
}
```

```
{
  "errors": [
    {
      "message": "Cannot query field \"dough\" on type \"Pizza\".",
      // error details
    }
  ]
}`
```

```
{
  "errors": [
    {
      "message": "Field \"pizza\" must not have a selection since type \"String!\" has no subfields.",
    }
  ]
}
```

```
{
  "errors": [
    {
      "message": "Field \"toppings\" of type \"Pizza\" must have a selection of subfields. Did you mean \"toppings { ... }\"?",
      "locations": [
        {
          "line": 6,
          "column": 7
        }
      ]
    }
  ]
}
```

What is the error given by the GraphQL query below?

```
query{
  pizzas {
   __typename
    ... on Pizza {
      id
      toppings {
        id
        topping
      }
      status
      pizza
      dough // this is invalid!
    }
  }
}
```

What is the error given by the GraphQL query below?
<pre><code>query{
 pizzas {
 __typename
 ... on Pizza {
 id
 toppings {
 id
 topping
 }
 status
 pizza
 dough // this is invalid!
 }
 }
}
</code></pre>

Test your knowledge about how GraphQL validation works.


Quiz on Validate GraphQL query

Test your knowledge about how GraphQL validation works.

Introduction

Getting to Know GraphQL

Queries

Mutations

Schemas and Types

Schema Validation

Schema Execution

Schema Introspection

GraphQL Best Practices

GraphQL Exam

Quiz on Validate GraphQL query