I think maybe you are confusing SQL's view of the model with the underlying mathematical Relational Model? A Table is a superset of a Relation. As Date mentions in the interview you can have QBE/ISBL be a better mapping to the underlying mathematical model.
Subset. You can build relations on top of tables, but not tables on top of relations. SQL falls short of the mathematical model. As it pertains to the topic at hand, whether or not that is significant is not something we have tried very hard to prove in practice.
Of course you can; it is in the very definition of the Table which is a manifestation of a Relation. Relationships (which can also be mathematical Relations) across Tables/Views are a different thing.
> hence it being a subset.
No, all Relations are Tables but not all Tables are Relations because of ordering, duplicates, nulls.
> Of course you can; it is in the very definition of the Table which is a manifestation of a Relation.
You said multiple relations earlier, which is what the comment was in reply to. Why the fliply-flopping?
> Relationships
Relation, not relations, not relationships. The struggle is real.
> all Relations are Tables
Yes, that's right, a relation is a table with additional constraints – a superset. Although not a strict superset as it does not carry ordering forward.
You seem to be confused between the mathematical definition of a Relation and the English usage of the word "Relation".
> You said multiple relations earlier, which is what the comment was in reply to. Why the fliply-flopping?
Read my definition above again; I said "multiple sets" and NOT "multiple relations" which is a very different thing. You understood it wrong.
> Relation, not relations, not relationships. The struggle is real.
Only for you. I have been very clear in the usage of my terms above. A Table encodes a Relation. Additionally, when you do a JOIN across Tables you are manifesting a "Relationship" (English usage) which may/may not result in a Mathematical Relation.
> a relation is a table with additional constraints – a superset.
No, If there are additional constraints on set A than on set B then A cannot be a superset of B but a subset.
