Yes! This! Exactly! There’s so much that _can be knowable_ with SQL based on the constraints of the _query_ (not just the relational model) that it should be po

Yes! This! Exactly! There’s so much that _can be knowable_ with SQL based on the constraints of the _query_ (not just the relational model) that it should be possible to know the characteristics of the data (and in some cases even the performance characteristics) just from type characteristics.