Very nice article, but I did not like the example data he was using.
The problem is that both population and tournament city could be dependent on year.
Population (obviously) changes from year-to-year, so either his original data is incorrect or he's recording a city's latest population along with all historic tennis championship winners -- neither interpretation makes a lot of sense. Why not use something unlikely to change such as either elevation or country?
Likewise, tournament city is not a fixed value for a tournament. For example, the Australian Open, which he uses as one of his examples, has also been set in Sydney, Adelaide, Brisbane, Perth, Christchurch (NZ), and Hastings (NZ).
To resolve this, he would either have to introduce a two column primary key (tournament, year), or pick some simpler data. I suggest the latter.
Even with all of this criticism, I think it's one of the cleanest introductions of the normal forms for beginners.
I clicked on your CV just because the link was available on the side, and I was shocked to find out that you're still in high school. There are professionals that would have taken 10x as long to explain it only half as clearly. For context, I've been in the business for ~25 years. Keep up the great work.
The problem is that both population and tournament city could be dependent on year.
Population (obviously) changes from year-to-year, so either his original data is incorrect or he's recording a city's latest population along with all historic tennis championship winners -- neither interpretation makes a lot of sense. Why not use something unlikely to change such as either elevation or country?
Likewise, tournament city is not a fixed value for a tournament. For example, the Australian Open, which he uses as one of his examples, has also been set in Sydney, Adelaide, Brisbane, Perth, Christchurch (NZ), and Hastings (NZ).
To resolve this, he would either have to introduce a two column primary key (tournament, year), or pick some simpler data. I suggest the latter.
Even with all of this criticism, I think it's one of the cleanest introductions of the normal forms for beginners.