An SQL "expert" with records with duplicate keys? That starts alarm bells ringing for me. Generally any SQL table should have a primary key which by definition must be unique for each record. Of course it's possible they have some sort of composite key based on multiple fields that needs combining to correspond to a unique page name in ProcessWire. There are certainly cases where I've build SQL tables with composite keys, with one scenario being many-many relationships, and that's something that Processwire doesn't handle too well, although there is a module that makes many-many type relationships possible, although it doesn't compare to what you can do with pure SQL.
Processwire does handle One-Many relationships fine via page reference fields or Pagetable fields.
If you really must have a direct relationship between SQL commands and table structure and your CMS, I actually wonder whether ProcessWire is your best option. I've been doing a bit of investigation of Directus which looks promising, although it's headless, so no templates for output like ProcessWire, just a REST API, from what I can see, no full text indexing, and being more of a direct SQL - CMS mapping, it also lacks the hierarchical parent-child structure that ProcessWire handles so well, as it doesn't make any assumptions about what sort of data structures you have, whereas ProcessWire, while generally very un-opinionated does treat everything as a page in a page hierarchy. For websites, that's generally a pretty reasonable assumption, but if you really don't want that, and just want pure SQL tables then there are alternatives. While something like Directus will give you a direct SQL to CMS mapping, it won't fix bad SQL data, so if you've already started down the ProcessWire path, you want to be really sure it's worth the effort to change.
I come from a pure SQL background myself, and it only took me about 20 minutes of reading the ProcessWire documentation to understand how it works, so I don't think it should be hard for someone from an SQL background to adapt. Maybe there's room for a blog post or tutorial showing how to "do it this way in SQL" and ProcessWire equivalent along with what's different.