How can "GROUP BY" act on non-column values?
There are 267 employees and 15 with last names starting with 'A'. What does this return?
SELECT COUNT(1) FROM EMPLOYEES GROUP BY 'A';
Steven Parker177,670 Points
It doesn't exactly "act on" the constant value, that's part of the point of the question. The fact that the grouping is not being done on a value related to any column determines what will be returned in the result.