Hacker News Reader

Comment by ransom1538 | Hacker News Reader

I have been doing mysql database type things for 15 years solid. Once during a job interview at digg.com, someone [ok ok doxx removed] asked: "what is a having statement in sql?". I jumped in explained how you can filter aggregated sets performed by a 'group by' and rambled on and on. He stopped me and said, "You can use a having statement without a group by, are you sure you know how they work." I have never seen this or done this in practice, so I just stood there stumped. He rolled his eyes and ended the interview. 4 hours of an amazing interview going well: ruined. At least this guy went on to ruin digg.com. "Let's just re-write everything over again better" kinda guy.

View on HN

Do you realize you dodged a bullet at that moment? That was a classic case of "smartest-guy-in-the-room" syndrome: from your description, he wasn't there to interview you, he was there to show off and stroke his own ego.

Be glad you didn't get that job, because that would have been the future of your days at work -- constantly listening to Mr. Smartypants compensate for his own sense of inadequacy, where every different opinion is treated as a personal insult or a challenge. No thanks. That personality type is infectious (not in a good way) and it damages an organization.

If I understand correctly from this post on dba [1], HAVING without GROUP BY would have the same effect as WHERE. Seems like they were just being pedantic for no good reason.

[1] https://dba.stackexchange.com/questions/57445/use-of-having-...

If one of the columns you're SELECTing has some sort of complicated expression in it (e.g. `UNIX_TIME(colA) - UNIX_TIME(colB) AS duration`), I think you can refer to that column by name in HAVING, but not in WHERE. It's a pretty niche thing though; I can't remember if I've ever actually used it.

I believe you’re correct.

However because HAVING takes place after all the results are fetched and processed (so it can do GROUP BYs) HAVING can’t use indexes.

So while the two will give you identical results if you’re not using a GROUP BY, the HAVING version could be thousands of times slower. Or worse.

How would this differ from contains?

This person probably wanted you to say that there might be a performance problem in filtering a result set using HAVING, instead if selecting rows using WHERE, if the query optimizer fails to see the equivalence. And the only reason why they knew was because they fixed that very same problem one week before, after debugging it for three days, as it is often the case with bad interview questions.

Edit: shouldn't assume gender

Have you ever seen anyone using having in place of where honestly?

I have definitely seen people confuse them, although not in production code.

Hm, I'm honest: If I get along well with an interviewee, I might throw technical oddballs at them like that. I wouldn't have known that specific one.

But at that point, I'm more interested in their personal reaction. Pondering, and/or asking "Why the fuck do you even do that!" would've been fine there to me.

honestly who cares? there is no sane reason to use having without group by.

[No longer applicable]

Naming a company and recounting an interview experience is not doxxing.

He named a specific person before the edit, which is a bit different. Nothing wrong with naming/shaming digg.com, though.

Naming a specific person is not nice, but still not "doxxing."

That's exactly what doxxing is.(Paraphrasing here) "This guy was really shitty in my job interview. Here's their LinkedIn page."

Seemed pretty cut and dry to me. What about it disqualified it as a not-doxxing situation?

I thought doxxing was the act of publishing the true identity of a person which was only known by their online handle before.

"Doxxing", in the original sense, involves publishing more private info, info like address, home phone, cell phone, SSN, etc. A link to someones public LinkedIn page is not a "dox."

That is an absurd definition of doxxing. Reporting the names of you have had in-person interactions with, in cases where it would not expose someone's pseudonym, is in no way, shape, or form doxxing.

Don't censor others.

Reply on news.ycombinator.com