GUID as primary key

Hi,

<Oracle 9.2i>

I got 2 questions:

Is there a package (or something else) where I can get a GUID from the oracle system? (something like SELECT DBMS_GUID.GenerateGUID FROM DUAL) We want to use GUID for all Rows in the Database. We can do this by the application, but sometimes (Triggers etc.) it would be useful to generate a GUID in the database directly.

You can give a column in a table a default value. How can I give oracle a function instead of a plain value so that this function is called everytime a new row is generated?

Thanks

Andreas

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