SQL recursive query that gets all ancestors of an item

Question

ID       parent_id   name
---------------------
1        2            first 
2        4            second
3        3            third
4        5            fourth
5          


        

Answer 1

You can use something like this:

with parents as 
(
  select ID, parent_ID
  from t
  where parent_ID is not null
  union all 
  select p.ID, t.parent_ID
  from parents p
    inner join t on p.parent_ID = t.ID
      and t.parent_ID is not null
      and t.ID <> t.parent_ID
)
select *
  , parents = '(' + stuff
    (
      (
        select ', ' + cast(p.parent_ID as varchar(100))
        from parents p 
        where t.ID = p.ID
        for xml path('')
      ), 1, 2, ''
    ) + ')'
from t
order by ID

SQL Fiddle with demo.

This combines two very common T-SQL techniques - using a CTE to get a hierarchy and using FOR XML PATH to get a CSV list.