> For the complete documentation index, see [llms.txt](https://docs.eduflow.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.eduflow.com/graphql/graphql.md).

# Introduction to GraphQL

## Query language

[GraphQL](https://www.graphql.org/) is a query language for API's. It's query language can pull multiple objects of different types, with less queries that would be needed using REST.

Where else is GraphQL used? Facebook, GitHub

#### What does GraphQL do?

REST API's follow a concept of [architectural constraints](https://en.wikipedia.org/wiki/Representational_state_transfer#Architectural_constraints). The classic API is multiple endpoints for various resources alongside `GET`, `POST,` `PUT` and `DELETE`.

GraphQL on the other hand usually has *one* endpoint, always `GET` or `POST`. The magic is in the query passed in the post data.

Assume the following:

```graphql
{
    institution {
        name
    }
}
```

Response:

```javascript
{
  "data": {
    "institution": {
      "name": "Happy University"
    }
  }
}
```

A couple things:

* The query to a single endpoint, via `GET` (`?query=...`) or `POST` (via `POST` data)
* The response is JSON
* The response structure matches the query

What's more is, GraphQL schemas enforce a structured, typed API, and provides instrumentation. This can best be put into example by seeing GraphiQL - a client for graphql - with the query above:

![](/files/-MRzwnCjnc1JBGbXtl1R)

## Core concepts

#### Queries and Mutations:

* Query: Usually reading
* Mutation: Usually create, updating or deleting

#### Basics

* [Fields](https://graphql.org/learn/queries/#fields)
* [Type system](https://graphql.org/learn/schema/#object-types-and-fields):
  * [Object types](https://graphql.org/learn/schema/#object-types-and-fields)
  * [Enums](https://graphql.org/learn/schema/#the-query-and-mutation-types)
  * [Lists](https://graphql.org/learn/schema/#lists-and-non-null)
  * [Interfaces](https://graphql.org/learn/schema/#interfaces)

#### Advanced

* [Variables](https://graphql.org/learn/queries/#variables): Optional parametrization
* [Fragments](https://graphql.org/learn/queries/#fragments): Repeatable pieces of query
* [Pagination](https://graphql.org/learn/pagination/): Traverse through lists of data