True, but COUNT(NULL) and COUNT(1/NULL) are not mentioned in the T-SQL COUNT() reference. Since the results of SELECT (1/NULL) is NULL, this would appear to be a way to pass the NULL value to COUNT(), but BOL doesn't mention it, nor is there any explanation of why the result of COUNT(1/NULL) would be zero. If I were to take a stab, I would guess that supplying NULL to the COUNT() function satisfies the parameter condition but does not count any rows. There may be some mathematical explanation of the behavior, but I wouldn't know what it is.