Data in table changed?

Hi all,

I have a large number of clients synchronizing with a central database.
The clients update their local data by polling the database for changes
at fixed intervals. I need an efficient way of determining if data in a
table has been changed (either updated, deleted or inserted). Can this
be achieved without scanning the tables using expensive SQL? (my tables
are _big_!) Is there some way to get a "time for last update" for a
specific table? Or something similar I can use?

Thank you :)

Kind regards,
Thomas Holmgren
Denmark


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Mvh.
Thomas Holmgren