What is GraphQL? An Introduction to Its Types, Use Cases, and Schema

What are the components of GraphQL?

GraphQL consists of several key components that work together to enable clients to request data from APIs in a flexible and efficient manner. The components include;

• Query language: GraphQL has its own query language through which clients can request data from the server.
• Schema: The schema is an important part of the GraphQL system that helps clients define the available data types and operations that can be performed on that data.
• Resolver function: The function is responsible for retrieving the requested data from one or more data sources, including databases, APIs, or other sources.
• Server: The server is where all the requests are received from the clients and is being processed.
• Client: The client is the component that sends requests to the server and receives responses for the data. A client can be a web or mobile application and use a GraphQL client library to interact with the server.

How do clients interact with a GraphQL server?

Usually, a client interacts with the GraphQL server by sending queries and mutations using the GraphQL query language. Here are the steps involved in a typical client-server interaction with GraphQL.

🔷 Define the query

The process of retrieving data in GraphQL involves clients defining their required information through the query language. The process enables them to specifically request the exact data they need, without having to go through irrelevant or unnecessary information and streamlining and improving the efficiency of data retrieval.

🔷 Send the query

When the client wants to send a query, they can use HTTP or WebSocket protocols. The query can be sent as a POST request with a JSON payload, or as GET request with the query trying as a URL parameter. The standardized protocols simplify the process of querying data from the backend systems and ensure that the applications are reliable and performing well for end-user.

🔷 Processing the query

The query is processed in the server against the GraphQL schema. The process allows effective communication between the client and server, ensuring relevant data is exchanged and is according to the pre-defined standards by the schema.

🔷 Retrieve data

When the server receives a request for data, it takes action and pulls the relevant information from different sources. The retrieval process ensures that users receive accurate and updated information each time they interact with the application.

🔷 Return response

After the data is retrieved, the server starts with the processing and formatting of data before sending the response back to the client.

🔷 Client retrieves response

When the server returns the response to the client, it gains access to the retrieved data. The client can use the retrieved data for various purposes such as rendering the user interface and carrying out important operations.

What is GraphQL schema?

GraphQL Schema is an essential component that helps in defining the structure of the data that can be queried or mutated by the client. The schema determines the types of data that can request, the relationship between the data, and entry points to access the data to the client.

The schema is usually defined through the Schema Definition Language (SDL) allowing the developers to define the types of queries and mutations processed by the API. The GraphQL Schema includes several components and we have listed them below;

🔹 Types
In GraphQL, types determine the shape and structure of the data that can be queried or mutated. The types can be in different forms such as a scaler, (e.g. String, Boolean, Int), object (e.g. User, Product), or custom types developed by the developers to fulfill the specific needs.

🔹 Field
Fields are an integral part of understanding how the information is structured in GraphQL. It includes three key elements such as name, a type, and an argument that help in filtering and sorting the data. The definition of fields within your project structure will help in creating an efficient system for accessing the relevant data.

🔹 Queries
Queries are the key building blocks for GraphQL which defines how data can be retrieved from the API. The operations can be performed and structured to request specific fields or sets of data in a flexible and efficient manner. With the help of queries, developers can create an interactive application that meets the user’s expectations.

🔹 Mutations
In GraphQL, mutations refer to the operations that are available to modify the data available in the database. The mutations carry out actions such as creating new entries or updating existing ones. This functionality poses greater control to the developers. With GraphQL mutations you can personalize the functionality of the application.

🔹 Subscription
Subscription acts like a backbone that provides clients with real-time updates. The subscriptions determine which operations can be subscribed and use to receive updates when its available. Such subscription functionality makes it possible for users to stay informed about changes and updates in the application.

What are the different types of GraphQL types?

When it comes to GraphQL, there are several types involved that can be defined in the schema. The GraphQL types define the shapes and size of the data that is required or mutated, and they can be used to model a wide range of data structures, from simple to complex objects.

Here are some of the common GraphQL Types;

• Scaler types
  The scaler types represent the most basic GraphQL types, and include primitive data values like strings, integers, booleans, and floats. GraphQL consists of various built-in scaler types, including String, Int, Boolean, Float, and ID.
• Object types
  The object types in GraphQL represent the complex objects which include multiple fields, like users, posts, or products. The developers can define custom object types to represent data in your API.
• List types
  Lists are essential to represent the array values of the programming. You can define the List Type by simply surrounding the data with a square bracket- [string], which will provide you with a list of strings. The list data can be stored and manipulated in a very convenient and efficient manner.
• Non-null types
  The non-null types are denoted by using an exclamation mark after the type like “String!”. The non-null types ensure the value is present and prevents the potential error that can occur in the code. The utilization of non-null types helps developers to be confident that the code is relevant and can execute seamlessly.
• Enum types
  The enum types offer a simple way to represent a fixed set of values in the code of the application. Enum type defines a specific list of values that are relevant to your application or program. The developers can create an enum type called “Color” and include significant options such as “RED, GREEN, and BLUE”. The enum type can make the code more organized and simple to read to ensure consistency for certain variables and parameters.
• Input types
  The input types have a similar purpose to object types, yet they are used as an argument while executing mutations instead of acting as fields in queries. Similar to object types, input types utilize the same structure to define when the “input” keyword is added. While creating a new user through a mutation, the input type “CreateUserInput” will be defined and implemented in the code.

What is GraphQL Query?

In GraphQL, a query is nothing but a request for specific data from the API. The GraphQL query determines the shape of the data that the client has requested, which can be retrieved from different schema.

The GraphQL Query works similarly to JSON object, with nested fields and arguments to specify which data is requested. There are three components of GraphQL query;

🔸 Query operations
The query operation is particularly used to retrieve data on the same server or API. On the other hand, a mutation operation modifies the data on that server or API. The subscription operation is to update in real-time so that the clients are provided with continuous information whenever it’s available. Through such segments of operations, developers can build interactive user-interface and other features in the applications.

There are several fields that can be used to refine the data or the results. The query field includes nested options, aliases for simplicity, arguments that filter the data, and fragments to reuse commonly used segments. The specification in your queries ensures that the results presented back are tailored relevantly to the request of data.

Once the query is submitted to the server, it responds with data in the JSON object that matches the structure of the request. The returned data offers insights and information that help in making an informed decision for the project. The data can be analyzed and interpreted carefully to unlock new opportunities and possibilities for growth.

How do you write a Query?

The query in GraphQL is written particularly in GraphQL query langauge, which is a textual representation of the data that the client wants to retrieve from the server.

Here is an example of a simple GraphQL query;