Hi, I'm the author. Yeah, you have a good point. Imperative programming was just the way that we were using SQL to build that system.
I've written something similar to the first part - extract raw data out of various source DB's using SQL queries then push it to our organisation's ERP product (SAP) using A2A messaging.
From my view SAP is black box but it handles the actual accounting/ financial logic part i.e Ledgers, product tracking, inventory management etc. Our Accountants all seem pretty comfortable using it.
We still use a general ledger to book the outputs of our new financial pipeline, but I don't think we have a traditional business model (no traditional inventory management). That's more in the finance and accounting department though, and I can't speak much to that.
We have been using it at the finance company I work for to maintain customer's ledgers.