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The weirdest thing about data science interviews (when I was actively interviewing) is SQL gotcha questions. Especially with window functions. Here's a long HN

The weirdest thing about data science interviews (when I was actively interviewing) is SQL gotcha questions. Especially with window functions. Here's a long HN thread a few months ago about an annoying situation with an interviewer asserting uncommon syntax is common: https://news.ycombinator.com/item?id=23053981 https://news.ycombinator.com/item?id=23053981 Another related SQL gotcha I saw multiple times is finding the top n records of each group in a table. Which is a know-it-or-you-don't implementation, and the interviewer can still be a jerk if they want by slamming the interviewee if they include ties, or not (RANK vs. ROW_NUMBER). It's telling that there aren't any SQL window function examples in this repo. Another fun aspect of SQL interviews is dialect-specific questions, particularly with how date/times are handled. Years ago, a company famous/infamous for primarily using mySQL explicitly noted in a take-home assignment problem definition that the database was PostgreSQL, which allowed them to ask the aforementioned window question problem, the AT TIME ZONE syntax for filter, and allow a specific definition for "beginning of week" which required me to download the database and test it manually.

claudeganon 6y ago
These kinds of stories seem insane to me. I currently have to do some data science-y stuff in the more generalist consulting dev role I have. I used to do a lot of SQL stuff years ago, but have forgotten most of the syntax beyond the basics. That being said, all it took is some minor googling and reading of a few blog posts to solve some middling hard problems for my client. What kind of companies make people jump through these nerd hoops? Do they actually have real work that needs doing or is this all just posturing by interviewers?
- gerbler 6y ago
  I think an element of it is that you can have unambiguous questions with SQL, which taken to the extreme do fall into gotcha territory. I was an interviewer for a business analyst & data science team recently and we needed to hire several analysts & data-scientists who had strong SQL skills because 90% of the data manipulation/processing used SQL. I was definitely aware that this limits who we hire, but we were very short-staffed and needed people so it was easiest for us to hire people who had a good understanding of SQL. That said, we did not care about syntax subtleties, just more if could you generally answer questions using SQL. And for the data-scientist role there was a lot more than just SQL but it was a useful check.
proc-iomem 6y ago
> Especially with window functions. Why are companies so bad at hiring?

claudeganon 6y ago

These kinds of stories seem insane to me. I currently have to do some data science-y stuff in the more generalist consulting dev role I have. I used to do a lot of SQL stuff years ago, but have forgotten most of the syntax beyond the basics. That being said, all it took is some minor googling and reading of a few blog posts to solve some middling hard problems for my client. What kind of companies make people jump through these nerd hoops? Do they actually have real work that needs doing or is this all just posturing by interviewers?

gerbler 6y ago
I think an element of it is that you can have unambiguous questions with SQL, which taken to the extreme do fall into gotcha territory. I was an interviewer for a business analyst & data science team recently and we needed to hire several analysts & data-scientists who had strong SQL skills because 90% of the data manipulation/processing used SQL. I was definitely aware that this limits who we hire, but we were very short-staffed and needed people so it was easiest for us to hire people who had a good understanding of SQL. That said, we did not care about syntax subtleties, just more if could you generally answer questions using SQL. And for the data-scientist role there was a lot more than just SQL but it was a useful check.

proc-iomem 6y ago

> Especially with window functions. Why are companies so bad at hiring?