The underlying problem here is that SQL lacks Sum Types (aka Tagged Unions). Such types solve all these problems effortlessly. In contrast to what SQL has, Sum

The underlying problem here is that SQL lacks Sum Types (aka Tagged Unions). Such types solve all these problems effortlessly. In contrast to what SQL has, Sum Types combined with Product Types (which is basically what a row is) are actually a universal way to model all possible data[0]. (Of course you may want syntax sugar, etc. on top of that, but Sums and Products at the bottom is sufficient.) [0] I'm actually not sure if I should qualify that -- I believe Sums+Products can actually model anything, assuming you allow recursive type definitions -- which might be hard to make perform well. Storing a linked list in a database field, e.g. might not be the best idea.