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Part II: GraphQL schema

GraphQL has its own type language that’s used to write GraphQL schemas - GraphQL schema language and it allows us to talk about GraphQL schemas in a language-agnostic way, since GraphQL can be used with any backend framework or programming language.

In a very simple form, a GraphQL schema looks something like this:

type Author {
  id: ID!
  name: String
}

This is a simple type definition of author model in our application. id and name are fields defined for the author model with their respective types.

Now lets build a simple schema for a blog app where our basic data requirements are as follows:

• Storing the profile data of each user
• Storing the article data and the author of each article
• Storing the likes given by users to articles
• Storing the comments written by users on articles

Create tables

As you would normally do with any relational database, data is modelled as tables.

Table	Columns
author	id, name
article	id, title, content, rating, author_id
like	user_id, article_id
comment	id, user_id, article_id, comment

Note: If you are using the hello-world quickstart, tables author and article have already been created via migrations

Note

With Hasura’s GraphQL engine, you don’t need to write your GraphQL Schema separately. It is automatically managed for you as you keep modifying the schema via the UI. Migration files will also be generated as you do this.

You can create tables via the API console.

Run:

# Run this command inside your project directory
$ hasura api-console

This will open up the API console and show you the API explorer page which you can use to understand the APIs provided by the data microservice.

Head to Data -> Add Table.

Create table like:

Create Table comment:

Create the author and article tables similarly if not already created.

Once these tables are created via console, the GraphQL schema for the same is generated by the Hasura data API.

Add foreign key constraints:

After creating the tables, the following foreign key constraints need to be set up to complete our data modelling:

• article::author_id -> author::id
• like::article_id -> article::id
• comment::article_id -> article::id

To add foreign key constraints, click on the table, go to the Modify tab and edit the columns for which you wish to add foreign keys.

Adding a foreign key constraint to the article_id of the like table:

Similarly, add the other foreign key constraints.

Note All of these schema related modifications will automatically reflect in GraphQL APIs.

Next: Explore the GraphQL APIs

Next, head to Part III: GraphQL APIs.

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