I once wrote a Sudoku solver in SQL in an afternoon because I was playing a Sudoku (a very newb player at that time) and it spontaneously occurred to me that all I was doing was a join or anti-join query repeatedly.
My data model was X,Y,V. Nothing nullable. Separately you need a table (possibly generated on the fly) of range 1 to 9. You wind up joining that a lot.
The whole program consisted of running INSERT INTO ... SELECT ... in a loop until 0 rows were inserted, indicating you were either done or you hit a point where no cell had a single solution. I'll spare everyone the rest of the details.
Incomplete, I know, but it fired the neurons, particularly with respect to the utility of the EXISTS expression in SQL.
I had no idea about things like "naked pairs" at that time, but I'm sure I could extend it to suport that.
It's interesting that if I translate that to a more traditional language, I independently came up with what is a cousin to Norvig's solution. I sure don't have his background, in fact my background is probably closer to Jeffries.
The main difference is that Norvig pre-enumerates all 9 possible values for all 81 cells then sieves them out, whereas my SQL constructs the 9*4 matrix from a temporary range 1..9 table, discovers the "must be" values, inserts those, then just repeats the process. Basically I'm Map whereas Norvig is Map> and the algorithm is slightly different.
My experience agrees with the author's. Incremental design does not work. Prototyping and being willing to throw away your prototype and do something wildly different has always been the better approach in my experience.
You wouldn't believe how many less experienced engineers I help with problems by coming in and approaching the problem with a fresh set of eyes. It takes years to build the skill and willpower to incinerate days or weeks worth of work in favor of an alternative solution you can write in an afternoon. But it's not a waste! If you gained enough insight from doing it the wrong way to be able to write it the right way, then you maximized the value of your time. It is actually a waste of your time to keep iterating on a fundamentally flawed design.