The following table lists the top 10 products by sales in the first couple of months of the year (the number of months will increase over time):

Find out the products that make the top 10 in every month of these months:

=spl("=transpose(?1).isect()",B2:E11)

Find out the products that make the top 10 once or more:

=spl("=transpose(?1).union()",B2:E11)

The calculation result is not given here because it is very long.

Find out the products that make the top 10 in January but fail to make the top 10 in any of other months:

=spl("=transpose(?1).diff()",B2:E11)

esProc Desktop and Excel Processing
8.1 Intersection, union and difference in the case of simple members - two sets
8.3 Intersection, union and difference in the case of row-based data - two sets - by key column