Not to mention actually using this schema ends up being really verbose since you have to do a bunch of joins. Additionally, besides being verbose, these joins can wreak havoc with the optimizer since join optimization is exponential. The optimizer might play nicely and just join all these on the ID column in whatever query you're doing, but that is very dependent on how the optimizer understands the input queries. Having a single table instead of 3 limits the number of ways the optimizer can think about a particular query.