Question

Let’s say I have the following table:

CustomerID ParentID Name ========== ======== ==== 1          null     John 2          1        James 3          2        Jenna 4          3        Jennifer 5          3        Peter 6          5        Alice 7          5        Steve 8          1        Larry  

I want to retrieve in one query all the descendants of James (Jenna,Jennifer,Peter, Alice, Steve). Thanks, Pablo.

Answer 1

On SQL Server 2005 you can use CTEs (Common Table Expressions) :

with Hierachy(CustomerID, ParentID, Name, Level) as ( select CustomerID, ParentID, Name, 0 as Level     from Customers c     where c.CustomerID = 2 -- insert parameter here     union all     select c.CustomerID, c.ParentID, c.Name, ch.Level + 1     from Customers c     inner join Hierachy ch     on c.ParentId = ch.CustomerID ) select CustomerID, ParentID, Name from Hierachy where Level > 0