How does a relational database work? (2017)

Since it’s a long and technical article that involves many algorithms and data structures, take your time to read it. If this time the algorithm needs to process 1 000 000 elements (which is not that big for a database):

I didn’t do the math but I’d say with the O(n2) algorithm you have the time to take a coffee (even a second one!) Like many useful algorithms, the merge sort is based on a trick: merging 2 sorted arrays of size N/2 into a N-element sorted array only costs N operations.

Source: coding-geek.com