To follow up further with my example. Let us call the act of taking
any RCOL(RnPK) and making them into attributes of any new view Rx,
Rotation.
- IS Rotation definable in terms of the basic relational operators of
SELECT, PROJECT, etc.
- Since Rotation MUST introduce empty data, unless the number of
elements in RCOL is the same for each RCOL for all RnPK, then:
- Should there not be something like NULL, but does not mean
undefined, but merely, empty?
- If it is provable that there exists cases where a resulting view is
not updatable, then, is not the case, that no database, regardless of
implementation, can actually satisfy the updateable view requirement?
- If in fact, the requirements for a relational database are
theoretically impossible to meet, because for any implementation you
can always create a non-updatable view, and, because, you have to
introduce NULL to do rotation, then, isn't fair to say that no
database can actually be a relational database?
Received on Sun Jun 22 2003 - 18:19:28 CDT
