Sorry, in my last message I forgot to explain how variables in GQL work…
Variables are defined by you when making the API call.
It gives you a way to use the same query but change some data at runtime. In the example, make the same change_column_value mutation but update what value is it.
Since GraphQL is a type system, you need to give each variable a type. If you give a type that doesn’t match the schema, it will give you an error.
Variables can be nullable vs non-nullable. ! means the variable is non-nullable. Effectively this means the variable is required.