What dataset isn't relational? Seriously. Even a basic chat software, you think Redis would be great for that. But what about when you want to relate users to m

What dataset isn't relational? Seriously. Even a basic chat software, you think Redis would be great for that. But what about when you want to relate users to messages? Actually, I've never worked on any project where our data set only needed simple key value mapping and no relationships at all.