The intent of this plugin is to showcase how to extend the WPGraphQL Schema using data from custom SQL tables.
A full tutorial about this code can be read here: https://www.wpgraphql.com/docs/using-data-from-custom-database-tables
wp-graphql/wp-graphql-notifications-connection-example
This is an example plugin showing how to register custom connections to WPGraphQL, pulling data from custom SQL tables.
PHP