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 environment is .NET and C#.

I’d like to be able to support any SQL Server 2000 SP4 or newer. My application is a bolt-on data visualization for another company’s product. Our customer base is in the thousands, so I don’t want to have to put in requirements that we modify the third-party vendor’s table at every installation.

By ‘changes to a table’ I mean changes to table data, not changes to table structure.

Ultimately, I would like the change to trigger an event in my application, instead of having to check for changes at an interval.

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The best course of action given my requirements (no triggers or schema modification, SQL Server 2000 and 2005) seems to be to use the BINARY_CHECKSUM function in T-SQL. The way I plan to implement is this:

Every X seconds run the following query:

SELECT CHECKSUM_AGG(BINARY_CHECKSUM(*)) FROM sample_table WITH (NOLOCK); 

And compare that against the stored value. If the value has changed, go through the table row by row using the query:

SELECT row_id, BINARY_CHECKSUM(*) FROM sample_table WITH (NOLOCK); 

And compare the returned checksums against stored values.

Answer 1

Take a look at the CHECKSUM command:

SELECT CHECKSUM_AGG(BINARY_CHECKSUM(*)) FROM sample_table WITH (NOLOCK); 

That will return the same number each time it’s run as long as the table contents haven’t changed. See my post on this for more information:

CHECKSUM

Here’s how I used it to rebuild cache dependencies when tables changed:
ASP.NET 1.1 database cache dependency (without triggers)