Обсуждение: Can a database notify all clients when something changes?

Can a database notify all clients when something
changes and send the changes to the clients?

Let me explain.
Suppose that there are 3 workstations connected to a
central database. When Workstation A changes
something, Workstation B and C must get the changes.

So, can any database do that? If it does, what is
called?

Is there a library for that?

Or Do I have to write 1 myself.( I hope not !  ).


thanx!



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Satan Devil wrote:
> Suppose that there are 3 workstations connected to a
> central database. When Workstation A changes
> something, Workstation B and C must get the changes.

Not really clear what you are trying to accomplish.  The simple fact
that all 3 workstations are communicating with a central database means
that they all "get the changes".  Are you saying that B and C might be
displaying the old version of data that A has just changed, and you want
B and C to automatically see the updated values?  If that is what you
are after, then you'll need to do something application-wise.  What
application are these clients using to view data?  You can either (1)
broadcast changes entirely through your application, or (2) set up a
trigger in the database to kick off the notifications.  Depending on how
many changes you want to monitor, solution 2 might be burdensome (lots
of triggers.)

--
Guy Rouillier

On Wed, Dec 15, 2004 at 03:37:05PM -0800, Satan Devil wrote:
> Can a database notify all clients when something
> changes and send the changes to the clients?

Sure.  Use LISTEN and NOTIFY.

--
Alvaro Herrera (<alvherre[@]dcc.uchile.cl>)
Al principio era UNIX, y UNIX habló y dijo: "Hello world\n".
No dijo "Hello New Jersey\n", ni "Hello USA\n".