This is mostly a hypothetical question, but it's something I've been tossing around and I wondered what other people though. Here's a contrived example to illustrate: Let's say I'm building an app that lets users pick a few keywords and then shows them photos that are tagged with those keywords.
On one hand, I could create
photo tables which store the data entities as they exist. This would let allow me to easily change the function of the app without needing to change the underlying data structures, but it also requires several queries to fetch the data I need for the app.
Or, I could just have a single
user-photos table, and somehow stuff all the data in there. This would make it easier to pull the data I need for the app, but it would be harder to perform any other type of querying on that data. After all, a
user-photo isn't really a thing -- it's just a convenient data structure for this one purpose.
This might be a bad example, but the main thrust of my question is: should your database structure be based on the actual underlying entities they're storing, or can you use shortcuts to make it easier to use the data for your purposes?