Auto assign old entries to parent category

Question

A client wants to clean up their messy categories, but when assigning the categories to parent categories, the entries don't update. So when I want to output a list of all entries in a parent category, I might get no results if the entries wasn't originally categorized with the parent category...

I realize there's an answer here: Automatically assign parent category to sub-category entries?

But that PHP-code does nothing for my entries, they're still only categorized with their original categories (which are now child-categories). Anybody got another PHP-code or an SQL-query to help me out?

Answer 1

I got a similar code-snippet as the one referred to in my question from Kevin at Ellislab. I couldn't get that one to work initially eiher, but after pruning the code, taking away some ' and " it worked perfectly. Here's the code that worked for me: cdpn.io/DAHeg