strategies for keeping an audit trail of UPDATEs

Hello,

In our app we must keep a trace of all changes (UPDATEs) done to an
important_table, so that it's possible to get a snapshot of a given
record at a given date.

The implementation strategy we are thinking about:

1. create an important_table_archive which inherits from
important_table,

2. create a trigger ON UPDATE of important_table which automatically
creates a record in important_table_archive containing only the UPDATEd
fields on the original record along with the modification date and
author and the primary key,

Is this a viable strategy for that kind of requirement? Is there a
better, more orthodox one?

Thanks in advance,

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