Comments on: MySQL Interview Questions: Wrong Answers Only

By: Daniel Nichter

Daniel Nichter — Fri, 08 Dec 2023 18:37:34 +0000

Would you really be able to alter a 10T table?

Yes, it’s a recently solved problem:

By: Kedar Vaijanapurkar

Kedar Vaijanapurkar — Fri, 08 Dec 2023 07:14:11 +0000

Hi “Art”,

As an interviewer I really like to understand the thought process more than the real answer. You know “love the journey more than the destination” thing 😉 it is sort of that. This gives us a picture of how much of a brainstorming the candidate can do.

Also, about “…if I actually want to join the organization I’m applying to. “, usually during an Interview, the interviewer might really pulling your nerves to test you, doing deliberate wrong counter arguments to get the better justification and so on. IMHO this is not really a good subject to base a decision.

About your response to Trivia question is not right. Here I’m playing with the word “Dual”.

MySQL has a single database object, which is actually double.
You can’t see either of them, yet you can query! What is that?
> “dual” is a table (object) but the meaning hints “double”
> you cannot see “dual” object by “show tables” or any other queries but you can query a “dual” table:

select "kedar" from dual;

1	select "kedar" from dual;

Finally, I’d share my blog about sql_generate_invisible_primary_key and its usefulness.

(BTW Art, I feel the comment is AI generated)

Thanks,
Kedar.

By: Art

Art — Thu, 07 Dec 2023 08:40:55 +0000

I can relate to answers 1 and 5 as I probably would have answered the exact same thing. As having been in the interview seats many times, whenever I get an open question like these two I tend to answer with a provocative answer. Normally this would lead to a discussion. Being a MySQL expert, I can leverage this discussion to determine if I actually want to join the organization I’m applying to. If the discussion is unsatisfactory I’ll simply decline the offer.

> MySQL has a single database object, which is actually double.
> You can’t see either of them, yet you can query! What is that?
I would say you are referring to the generated invisible primary key. If the sql_generate_invisible_primary_key is enabled, a table without a primary key will automagically have one created. This creates both an invisible column with an auto increment attached to it and an invisible primary key. This means you can’t see either of them, but you would be able to select a specific row (or rows) by querying this column explicitly.