Get entire chain of IDs in self-referencing table given any ID in hierachy
I have a table that contains the following data:
+--开发者_JS百科--+----------+
| ID | ParentID |
+----+----------+
| 27 | 0 |
| 38 | 27 |
| 45 | 38 |
| 86 | 0 |
| 92 | 45 |
| 48 | 86 |
| 62 | 92 |
| 50 | 62 |
-----------------
I would like to be able to pass any ID to a stored procedure and get the entire chain of IDs (parents and children) of that given ID.
ie. if I pass ID = 45, I should get:
27
38
45
92
62
50
Similarly, if I pass ID = 86, I should get:
86
48
Any help would be greatly appreciated!
You can use two recursive CTE's. The first finds the root node and the second builds the chain.
declare @T table(ID int, ParentID int)
insert into @T values (27, 0), (38, 27), (45, 38), (86, 0),
(92, 45), (48, 86), (62, 92), (50, 62)
declare @ID int = 45
;with cte1 as
(
select T.ID, T.ParentID, 1 as lvl
from @T as T
where T.ID = @ID
union all
select T.ID, T.ParentID, C.lvl+1
from @T as T
inner join cte1 as C
on T.ID = C.ParentID
),
cte2 as
(
select T.ID, T.ParentID
from @T as T
where T.ID = (select top 1 ID
from cte1
order by lvl desc)
union all
select T.ID, T.ParentID
from @T as T
inner join cte2 as C
on T.ParentID = C.ID
)
select ID
from cte2
Version 2
A bit shorter and query plan suggests more effective but you never know without testing on real data.
;with cte as
(
select T.ID, T.ParentID, ','+cast(@ID as varchar(max)) as IDs
from @T as T
where T.ID = @ID
union all
select T.ID, T.ParentID, C.IDs+','+cast(T.ID as varchar(10))
from @T as T
inner join cte as C
on (T.ID = C.ParentID or
T.ParentID = C.ID) and
C.IDs+',' not like '%,'+cast(T.ID as varchar(10))+',%'
)
select ID
from cte
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