Hi,

As with any unbalanced compare, the performance varies.

Just compare this method with use your favorite compare and look closely at the execution plan

In my query close to 50% of the time is spent reading the 2 source tables using a clustered index scan, which is the most efficient way to read the ENTIRE table content.

The Merge join that does the actual compare work is only 19 % of the time

The rest: 33%, is spent storing the result.

If you find a more efficient way, i'd be happy to review your code!

Theo 🙂