Thanks for helping out!
The following query will use placeholders (NULL) if an element is not part of the grouping set.
From what I understand is that columns can be NULL or have an value.
I only 'see' two possible values:
1) a shipping city is filled in, for instance with the value 'xxx'
2) nothing is filled in, thus it's NULL, unknown.
3) what is the third??
What does it mean "an element is not part of the grouping set" ?
SELECT shipcountry, shipregion, shipcity, COUNT(*) AS numorders
GROUP BY ROLLUP( shipcountry, shipregion, shipcity );