Question

I’m dealing with a large multi-national corp. I have a table (oldtir) that shows ownership of subsidiaries. The fields for this problem are:

• cID – PK for this table
• dpm_sub – FK for the subsidiary company
• dpm_pco – FK for the parent company
• year – the year in which this is the relationship (because they change over time)

There are other fields, but not relevant to this problem. (Note that there are no records to specifically indicate the top-level companies, so we have to figure out which they are by having them not appear as subsidiaries.)

I’ve written the query below:

with CompanyHierarchy([year], dpm_pco, dpm_sub, cID)
as (select distinct oldtir.[year], cast(' ' as nvarchar(5)) as dpm_pco, oldtir.dpm_pco as dpm_sub, cast(0 as float) as cID
    from oldtir 
    where oldtir.dpm_pco not in 
       (select dpm_sub from oldtir oldtir2 
          where oldtir.[year] = oldtir2.[year]
            and oldtir2.dpm_sub <> oldtir2.dpm_pco)
      and oldtir.[year] = 2011
    union all 
    select oldtir.[year], oldtir.dpm_pco, oldtir.dpm_sub, oldtir.cID
    from oldtir 
      join CompanyHierarchy
        on CompanyHierarchy.dpm_sub = oldtir.dpm_pco 
        and CompanyHierarchy.[year] = oldtir.[year]
      where oldtir.[year] = 2011 
             )

select distinct CompanyHierarchy.[Year], 
       CompanyHierarchy.[dpm_pco], 
       CompanyHierarchy.dpm_sub, 
   from CompanyHierarchy
   order by 1, 2, 3

It fails with msg 530: “The maximum recursion 100 has been exhausted before statement completion.”

I believe the problem is that the relationships in the table aren’t strictly hierarchical. Specifically, one subsidiary can be owned by more than one company, and you can even have the situation where A owns B and part of C, and B also owns part of C. (One of the other fields indicates percent of ownership.)

For the time being, I’ve solved the problem by adding a field to track level, and arbitrarily stopping after a few levels. But this feels kludgy to me, since I can’t be sure of the maximum number of levels.

Any ideas how to do this generically?

Thanks,
Tamar

Answer 1

Thanks to the commenters. They made me go back and look more closely at the data. There were, in fact, errors in the data, which led to infinite recursion. Fixed the data and the query worked just fine.