Comment by rramadass
1 year ago
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.
> A Table is a superset of a Relation.
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.
Not quite true - https://en.wikipedia.org/wiki/Table_(database)#Tables_versus...
A Table is a Relation encoded as a set of tuples resulting from the cartesian product of values from multiple sets each of which is from a domain.
Tables are a weaker form of Relations and hence a superset except for the "ordering" characteristic when it can be considered a subset.
> multiple sets
Right. As before, you cannot build a table on top of a relation. You can build a relation on top of a table, though.
> Tables are a weaker form of Relations
Yes, exactly, hence it being a subset.
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