virtual (COMPUTED BY) columns?

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Hi.

These fields do not use any disk space, as the data in them is
derived on the fly.

For example:
CREATE TABLE T_EXAMPLE (
SOME_DATE DATE,
JDATE     COMPUTED BY EXTRACT(JULIAN FROM SOME_DATE)
);

A work-around is to create a function, and reference it in every
query, but storing them in the table definition is the "tidy",
low-maintenance way to do it.

Thanks
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