[Tfug] more RDBMS

[Bexley Hall]

Hi,

I *hope* these are simple RDBMS questions (even
though the simple ones never actually *prove* to
be so!  :< )

Question primo:

I'm looking for an inexpensive (computationally)
way to see if a "database", or, specifically, a
certain *table* has been *changed* since the last
time I "noticed" it.  I.e. a way of stat(2)'ing
it that is *portable* (i.e. lives in SQL land).

Essentially, I need to do an expensive query
but *only* if the dataset has changed since the
last time I ran that query.  (presumably, I ran
it last time *because* the dataset had changed!)
I.e., I do some client-side caching...

Question secundo:

In a VERY LIGHT DUTY APPLICATION, how foolish is
it for clients to periodically issue queries of
the RDBMS like:

  SELECT now;

instead of tracking time "locally", themselves?
I.e., use the RDBMS as a time reference instead
of burdening the individual clients (which, in
this case, are kiosks) with the overhead of a
"real" time service?

Thanks!
--don

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