How to get the last non empty value of a hierarchy? - sql

Question

I've got a hierarchy with the appropriate value linked to each level, let's say :
A 100
A1 NULL
A2 NULL
B
B1 NULL
B2 1000
B21 500
B22 500
B3 NULL
This hierarchy is materialized in my database as a parent-child hierarchy
Hierarchy Table
------------------------
Id Code Parent_Id
1 A NULL
2 A1 1
3 A2 3
4 B NULL
5 B1 4
6 B2 4
7 B21 6
8 B22 6
9 B3 4
And here is my fact table :
Fact Table
------------------------
Hierarchy_Id Value
1 100
6 1000
7 500
8 500
My question is : do you know/have any idea of how to get only the last non empty value of my hiearchy?
I know that there an MDX function which could do this job but I'd like to do this in an another way.
To be clear, the desired output would be :
Fact Table
------------------------
Hierarchy_Id Value
1 100
7 500
8 500
(If necessary, the work of flatten the hierarchy is already done...)
Thank you in advance!

Answer 1

If the codes for your hierarchy are correct, then you can use the information in the codes to determine the depth of the hierarchy. I think you want to filter out any "code" where there is a longer code that starts with it.
In that case:
select f.*
from fact f join
hierarchy h
on f.hierarchyId = h.hierarchyId
where not exists (select 1
from fact f2 join
hierarchy h2
on f2.hierarchyId = h2.hierarchyId
where h2.code like concat(h.code, '%') and
h2.code <> h.code
)
Here I've used the function concat() to create the pattern. In some databases, you might use + or || instead.