Not OP, but we often include these two in our interviews:

1. Write code that will find the second largest item in an array on ints.

2. Write SQL that selects the second highest number from a DB table.

I'm floored how few candidates can do these. Many end up giving up or fiddling for 10 minutes before giving something like `SELECT table WHERE 2`.

wouldn't be surprised people miss the SQL question. Full stack devs are rather rare nowadays, and it's a bit obscure SQL trivia considering the answer is dependent on which SQL db you're using.

Modulo syntax/keywords, I think the following query would work in any modern dialect:

    SELECT num FROM 
        (SELECT num FROM nums ORDER BY num DESC LIMIT 2)
    ORDER BY num ASC LIMIT 1;

which is actually nearly identical to the simplest Python solution in terms of the computation that's specified:

    lambda xs: None if len(xs) == 0 else sorted(xs)[-2:][0]

I think the reason the question is tricky for some is because they either:

1) haven't used SQL in a long time and forgot all the syntax, or else

2) don't really "grok" SQL as a model of computation (as opposed to e.g. a data structuring language or something like that).

But both of those seem like good reasons to disqualify someone from a full stack role?

A common reason in my experience is that the things they've built were done very slowly. I've failed my share of interviews because I was having a bad day, certainly, but I have direct professional experience with many people who require hours of dedicated working time to produce even the simplest of pull requests. This isn't a complete justification (if I have professional experience with them doesn't that mean they passed our straightforward coding tests somehow?), but I do think that there's a real selection problem there people are trying to solve.