Hierarchies

Hi

I understand that data in a hierarchy must be unique

2012 <- Dec 2012 <- Dec 26 2012

that is, when I talk about "Dec 26 2012"
I'm talking about "Dec 2012", and "2012" too

Another typical example is a hierarchy of employees
in that case, I don't know what happen
if an employee works for more than one department
but I suspect that it should not be a hierarchy

my first question is if is it a hierarchy or not

my second question is if doesn't it affect aggregations

in third place, I present you my case
I have a fact table of courses, telling how much students of each course
have passed the final exam, and how much they still ought the exam

- sk year
- sk course
- passed
- ought

there is not uniqueness, because a course may appear in several years

I'm thinking in making a degenerate dim "year-course" for giving some uniqueness

- sk year
- sk year-course
- sk course
- passed
- ought

the hierarchy would be "year<-year-course" or "course<-year-course"

is this a usual, normal, efficient in terms of resources, solution?

Am I very very wrong???


thanks in advance for clarifying me!!

I'm sorry
I missunderstood some concepts

I'll repost later