Re: database sorting algorithms.

Thanks a lot.
I found out about this Youtube video (https://youtu.be/alJswNJ4P3U?t=1852)
in case you guys are interested.
This video really clarify about the time complixty of MergeSort.

On Sat, May 1, 2021 at 3:19 PM Gavan Schneider <list(dot)pg(dot)gavan(at)pendari(dot)org>
wrote:

> On 1 May 2021, at 17:06, Jian He wrote:
>
> Been self study Database, from database I deep dived into sorting
> algorithms.
>
> Databases can do in-memory QuickSort. It also has an on-disk MergeSort.
>
> For MergeSort: I follow this tutorial https://youtu.be/6pV2IF0fgKY?t=1108
> (around 1 minutes only)
>
> Also check https://en.wikipedia.org/wiki/Merge_sort
>
> But I am still not fully understanding about *nlogn*. I understand how
> many
> passes it will take, that is* logn. *
> Yes each pass will sort N elements.
> But I still don't get the *N* stand f*or in n*logn.*
>
> So, answering the question…
> The ’n’ refers to the need to do something to each element at least once,
> so the sort time grows in simple proportion to the size of the list that
> needs to be sorted. Unfortunately that is not enough work to get the list
> sorted so extra steps are needed. The log(n) indicates how many extra steps
> are needed. So the overall performance is proportional to the number of
> elements (N) multiplied by the log of the number of elements, viz., N *
> log(N)
>
> Regards
> Gavan Schneider
> ——
> Gavan Schneider, Sodwalls, NSW, Australia
> Explanations exist; they have existed for all time; there is always a
> well-known solution to every human problem — neat, plausible, and wrong.
> — H. L. Mencken, 1920
>