hi ... nice examples, but this seems useless ...

(select name, count(age) as agen, max(age) as agemx /* Count & Max */
from sashelp.class where age > .
group by age
) as c on a.name=c.name

since if you group by AGE, the MAX(AGE) will just be the AGE that's already in each observation of the original data set ... so AGEMX always is the same value as AGE