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In the SQL statements you write, you
may refer to a subtype as if it were a separate table. From a
subtype, you can select:
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All columns of the subtype. |
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All subtype indicators of the constellation, since these are
attributes of the supertype. |
This applies whether your
subtype data is stored in the same table as the supertype data or
in separate database tables. Set the Create Separate Tables
attribute to determine how subtype data should be stored.
EXAMPLE 1:
If Persons can be Guides, then:
SELECT *
FROM guide
will not only select ALL Guide
(subtype) attributes table but also ALL Person (supertype)
attributes.
EXAMPLE 2:
If Persons can be Guides or Staff (subtype set Occupation), and
they can be Male or Female (subtype set Gender), then you can
retrieve all highly experienced female guides with the following
statement:
SELECT *
FROM guide
WHERE experience = 'High'
AND female = 'Y'
In this example, Female is a
subtype indicator of the Person supertype table.
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