I’ve encountered a problem when I had to create 2 columns in one table and then copy values to those columns from another table with relation to id from the first table. This sounds complex, but it appears to be an easy one. I’ve also encountered such problem at my first job. The saddest thing is that neither I nor my team lead was able to solve it. Encountering it again wasn’t a big pleasure, even though I have much more experience than I had. And I decided to solve it.