SELECT * FROM depdetail WHERE  postingdate = '2016-01-07' AND LEFT(store,4) =  @comp_code

This works.

There's another table called company.
The company table has a column called comp_group, which can be blank or contain the code of another row in the table (comp_code)

It's a way of grouping related companies for reporting.

In addition to the rows pulled above, I'd like the query to pull any rows of related companies.

I can do it in the .NET app by looping, but I'd like to do it with a query if possible.

Any ideas?