It is a quiz that Triplebyte gave to programmers and they got a lot of responses so the data/article is interesting.
The first question is a SQL question. Make sure you can answer it! :)
I tend to harp on the SQL knowledge because I think it is soooo fundamental.
These questions are the same kind of questions I ask programmers/techies that I interview. Just watching their responses and how they think or body language gives me a good idea about where they are on a technical scale.