and similarly for tables telephone and employee. There is actually no need to use the
same name, room_no, in all three tables. For example, the room_no column in the
employee table could have been called office_no and declared as:
office_no room_type
The FOREIGN KEY, room_no, in the employee table would also need to be changed
to office_no.
SQL92 provides a weak form of domain which only partially implements the
relational model’s concept of domain. A stronger version would restrict operations
such as join to columns that share the same domain.
Question
1.Why might different domains be declared for telephone.room_no and
room.room_no?(2 min)
'HIDXOWV ...
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