|
A supertype is a
"constellation" of data in which the common attributes are defined
as the supertype (or generalization), with variable additions (or
specializations) for the subtypes.
For example, if Person is the
supertype, Staff and Guide are possible subtypes.
Authorization is defined on
the tables and columns defined in the Tables window of the Definer.
Whether a table is part of a subtype tree (or constellation) is
irrelevant. However, you must bear the following in mind:
|
·
|
The subtype indicator columns are included in the supertype
tables. This means that you can also give rights on these subtype
indicator columns. |
|
·
|
The primary-key columns of the supertype are shown in all
subtype tables. Although it is possible to define different rights
for these columns in super- and sub-type tables, it is only useful
to define it in the uppermost supertype table. Conceptually these
columns are considered to be the same in the whole subtype
constellation: defining authorization for primary key columns in
subtypes is ignored. |
|
·
|
Conditions on the rights on subtype tables and their columns
can also contain columns of their supertype(s). |
Related Topics:
How INSERT Statements are
Handled
How DELETE Statements are
Handled
How UPDATE Statements are
Handled
|
