• Nice question, and easy to get the "right" answer given the choices available. A small niggle is that the genuinely right answer ("It depends: 16 key columns if the table has no xml indexes, 15 key columns if there are any xml indexes") wasn't an option, but that shouldn't have lead to anyone picking any of the thoroughly wrong options.

    (Incidentally, I regard the introduction of XML into SQL in the way it has been done as a horrible mistake, and allowing it to interfere with cluster key column count limit in this was is really stupid.)

    Tom