You don't go through entire loops everywhere because if there isn't a match in the first two tables, you don't have to check the match with the third table.
It's better to check A x C before A x B if you know that A x C has less matching rows, because the final loop will be shorter.
Ah, I see the numbers in the example are the numbers of matched rows, not a total number of rows... Make sense. I do not work with databases, did not know that you should pay attention to the order here.
It's better to check A x C before A x B if you know that A x C has less matching rows, because the final loop will be shorter.