In this example, the database does not depend on the application -- and it would be smelly code if it did. Rather, you've abstracted the database into an interface and now inject the appropriate concrete implementation into the application, instead of constructing the concrete implementation in the application. Dependency inversion is almost always more appropriately phrased as dependency injection -- for exactly the reasons in this post (you've injected, but not inverted, which is exactly the right thing to do here).
I note that this example is also a great demonstration of the single responsibility principle, which you explain in the text (what if you want to change to a different database implementation?).
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In this example, the database does not depend on the application -- and it would be smelly code if it did. Rather, you've abstracted the database into an interface and now inject the appropriate concrete implementation into the application, instead of constructing the concrete implementation in the application. Dependency inversion is almost always more appropriately phrased as dependency injection -- for exactly the reasons in this post (you've injected, but not inverted, which is exactly the right thing to do here).
I note that this example is also a great demonstration of the single responsibility principle, which you explain in the text (what if you want to change to a different database implementation?).