Check for changes to an SQL Server table?

Question

How can I monitor an SQL Server database for changes to a table without using triggers or modifying the structure of the database in any way? My preferred programming enviro

Answer 1

How often do you need to check for changes and how large (in terms of row size) are the tables in the database? If you use the CHECKSUM_AGG(BINARY_CHECKSUM(*)) method suggested by John, it will scan every row of the specified table. The NOLOCK hint helps, but on a large database, you are still hitting every row. You will also need to store the checksum for every row so that you tell one has changed.

Have you considered going at this from a different angle? If you do not want to modify the schema to add triggers, (which makes a sense, it's not your database), have you considered working with the application vendor that does make the database?

They could implement an API that provides a mechanism for notifying accessory apps that data has changed. It could be as simple as writing to a notification table that lists what table and which row were modified. That could be implemented through triggers or application code. From your side, ti wouldn't matter, your only concern would be scanning the notification table on a periodic basis. The performance hit on the database would be far less than scanning every row for changes.

The hard part would be convincing the application vendor to implement this feature. Since this can be handles entirely through SQL via triggers, you could do the bulk of the work for them by writing and testing the triggers and then bringing the code to the application vendor. By having the vendor support the triggers, it prevent the situation where your adding a trigger inadvertently replaces a trigger supplied by the vendor.