Russell Wallace (ru*************@gmail.com) writes:
Suppose a database server and client are separated by a low bandwidth
link such as DSL, and the client repeatedly issues a query for, say, a
current product list.
Suppose the product list is large, but only a handful of entries have
typically changed between queries. It would be nice if only the changes
from last query to current one could be sent, saving bandwidth.
Is there any way to do this?
You would need to add a column to track changes. One way to do this is
to use a timestamp column. A timestamp column is automatically updated
when a row is touched with a database-unique 8-byte value that grows
monotonically. Thus, you can save the highest timestamp value client-
side, and then send this as a parameter the next time.
Note that this scheme as I descibed it, is not suitable for tables with
a high transaction-rate, as you may fail to read some updates.
--
Erland Sommarskog, SQL Server MVP,
es****@sommarskog.se
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