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I'm asking this question in a separate thread and it is in response to
Olu's question about the table. It does make sense to have an oracle
datatype for a mapping row doesn't it??
For example in the class object, "professors" has to be entered as a
name of a prof. but we have a "mapping" with the person table because
for example a professor can be associated with many classes and vice
versa. and we need to know about this mapping because exercise three
asks us to create these mapping tables.
If this understanding is wrong then I am thoroughly confused..does
"link" mean "references"?? If not, do we have to have "references" as
"extra_sql" for the professors column in the class object?
Thanks in advance for any help and clarifications.
-- ahmed ait-ghezala, November 6, 1999
A "link" is a row in a mapping table associating one object with another. You wouldn't put in any EXTRA_SQL associated with this mapping. There will be REFERENCES constraints but they'll be in the mapping table CREATE TABLE statement (pointing to the object tables).
-- Philip Greenspun, November 6, 1999