Here's how to use ActiveRecord to query a JSON column in MySQL.
In this example we have a json column
user_settings. We want to find which records have
theme set with a value.
Model.where("JSON_EXTRACT(user_settings, '$.theme') IS NOT NULL").count
JSON_EXTRACT is the most common MySQL function that I use. You have other options as well, they are all listed in the docs here.
Indexing JSON columns
If this is a common query you are running, you should index it. Learn how from this blog post: Index JSON in MySQL.