How do I write this query?

Databases
1

I’m trying to put a query together, but my brain is failing me. Here’s the simplified version of my schema;

ORGANISATION
id
name

NOTE
id
organisation_id
category
subcategory

For a given organisation, I want to find the note category/subcategory combinations that the organisation DOESN’T have.

For example, ‘Smith Industries’ might have notes about Pie/Baking, but no notes about Cheese/Disposal or Cheese/Production. So for ‘Smith Industries’, I want the output ‘Cheese/Disposal’ and ‘Cheese/Production’.

All note categories and subcategories are already known and defined, i.e. users can’t invent them on the fly.
Any help appreciated, this is confusing the hell out of me.

2

you’ll need a LEFT OUTER JOIN to match the categories/subcategories against the notes

you say the categories/subcategories are already defined… where are they? which table?