Hello,
on page 51ff of the most recent MEAP edition you mention that primary keys must be immutable. That statement qualifies at best as your personal opinion, but it is not true as a general rule. The SQL standard does not impose such a requirement, neither does any of the RDBMS that I know of.
SQL even provides a "ON UPDATE CASCADE" clause to cater for primary keys that are pointed to by foreign keys, which again goes against the statement from page 52 "Changing the value (or even definition) of a primary key, and all foreign keys that refer to it, is a frustrating task". Frustrating for who?
regards,
Christian Sell
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