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.
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.
They didn't happen to put a last-modified timestamp on their rows, did they?
Checksums can and will fail eventually. If your system accepts that two different sets of data will result in the same checksum, than you are fine. For that reason, I had to move away from checksums in most of our systems...
That's not actually an answer, it's a "your suggestion doesn't work".
This can be remedied for duplicated data by using the DISINCT keyword before the BINARY_CHECKSUM. There are a few other pitfalls discussed here but not exactly common scenarios.
The question is about changes in table data and information_schema contains schema (column definitions) of the table.