In doing some fairly small-scale data massaging/cleaning, involving JOINing a couple of tables, an early, erroneous attempt at a solution was drastically slower than (what I believe is) the correct one. I'm wondering if asking why the incorrect query was so slow would be on-topic here, or would it fall foul of the "too simple" rule (and should, instead, be asked on SO)?
I have read How do we define a question as being “too basic”? Where do we draw the line? and its answers. With respect to the first link of the first answer (leading to this answer) I am at best an "intermediate with aspirations" than a seasoned professional; but with respect to the the original question's second answer, while it isn't a particularly complex join, my question would not be about how to do the join, but why one version is so much slower than the correct one.