That’s one of the insights that Everyone Should Have about RDBs and SQL. Relational databases are about, well, relations, in particular the sort of discrete rel

That’s one of the insights that Everyone Should Have about RDBs and SQL. Relational databases are about, well, relations, in particular the sort of discrete relations that can be represented as a set of tuples. It doesn’t matter where those sets of tuples come from. From the disk? Great. Computed on the fly? That’s fine too. And by manipulating relations you get… new relations! What RDBs and SQL are actually about is composing relations in the way that, say, Haskell is about composing functions. And indeed the theory behind RDBs is called relational algebra.