Recursive CTE - recalculate the tree after exclusions - sql

Question

Lets say I have a table called #OrgList
CREATE TABLE #OrgList (
OrgUnitId int,
ParentOrgUnitId int,
PersonId int,
isExcluded bit
);
INSERT INTO #OrgList(OrgUnitId, ParentOrgUnitId, PersonId, isExcluded) VALUES
(1, NULL, 100, 0), (2,1, 101, 0), (3,1,102,0), (4,2,103,1), (5,2,104,0), (6,3,105,0), (7,4,106,0), (8,4,107,0), (9,4,108,0), (10,4,109,0), (11,4,110,1), (12,11,111,0)
My hierarchy tree structure looks like this
and my cte like this:
;
with cte as (
select OrgUnitId, ParentOrgUnitId, PersonId, isExcluded , 0 as level_num
from #OrgList
where ParentOrgUnitId is null
UNION ALL
select o.OrgUnitId, o.ParentOrgUnitId, o.PersonId, o.isExcluded , level_num+1 as level_num
from #OrgList o
join cte on o.ParentOrgUnitId=cte.OrgUnitId
)
select * from cte
I exclude OrgUnitId=4 and =11, then I want to update my recursive query that will recalculate the tree and show the new tree details, including level moves (there can be more levels and more consecutive exclusions, of course except the root node):

Answer 1

You should just add a second UNION ALL in your cte:
with cte as (
select OrgUnitId, ParentOrgUnitId, PersonId, isExcluded , 0 as level_num
from #OrgList
where ParentOrgUnitId is null
UNION ALL
select o.OrgUnitId, o.ParentOrgUnitId, o.PersonId, o.isExcluded , level_num+1 as level_num
from #OrgList o
join cte on o.ParentOrgUnitId=cte.OrgUnitId
where cte.isExcluded = 0
UNION ALL
select o.OrgUnitId, cte.ParentOrgUnitId, o.PersonId, o.isExcluded , level_num as level_num
from #OrgList o
join cte on o.ParentOrgUnitId=cte.OrgUnitId
where cte.isExcluded = 1
)
select * from cte

Answer 2

My approach:
Extend your initial CTE with an exclusion counter (ExclusionCount), counting the number of excluded nodes going from root to leaf nodes.
Add another recursive CTE to construct the upward path (cte_upwards) for each leaf node. Now decrement the counter added in the initial CTE.
Use a cross apply to select the first node where the upward path reaches an exlusion count of zero.
Solution:
with cte as -- initial CTE
(
select OrgUnitId,
ParentOrgUnitId,
PersonId,
IsExcluded,
convert(int, IsExcluded) as 'ExclusionCount', -- new counter
0 as 'level_num'
from #OrgList
where ParentOrgUnitId is null
union all
select o.OrgUnitId,
o.ParentOrgUnitId,
o.PersonId,
o.IsExcluded,
cte.ExclusionCount + convert(int, o.isExcluded), -- increment counter
cte.level_num + 1
from #OrgList o
join cte on o.ParentOrgUnitId = cte.OrgUnitId
),
cte_upwards as
(
select cte.OrgUnitId,
cte.ParentOrgUnitId as 'NewParentOrgUnitId',
cte.IsExcluded,
cte.ExclusionCount,
cte.level_num
from cte
where cte.ParentOrgUnitId is not null -- only leaf nodes (not a root)
and not exists ( select top 1 'x' -- only leaf nodes (not an intermediate node)
from cte cp
where cp.ParentOrgUnitId = cte.OrgUnitId )
union all
select cte_upwards.OrgUnitId,
cte.ParentOrgUnitId,
cte.IsExcluded,
cte_upwards.ExclusionCount - cte.IsExcluded, -- decrement counter
cte.level_num
from cte_upwards
join cte
on cte.OrgUnitId = cte_upwards.NewParentOrgUnitId
)
select cte.OrgUnitId,
cte.ParentOrgUnitId,
cte.IsExcluded,
x.NewParentOrgUnitId,
coalesce(x.NewParentOrgUnitId, cte.ParentOrgUnitId) as 'Recalculated'
from cte
outer apply ( select top 1 cu.NewParentOrgUnitId
from cte_upwards cu
where cu.OrgUnitId = cte.OrgUnitId
and cu.ExclusionCount = 0 -- node without excluded parent nodes
order by cu.level_num desc ) x -- select lowest node in upwards path
order by cte.OrgUnitId;
Result:
OrgUnitId ParentOrgUnitId IsExcluded NewParentOrgUnitId Recalculated
----------- --------------- ---------- ------------------ ------------
1 NULL 0 NULL NULL
2 1 0 NULL 1
3 1 0 NULL 1
4 2 1 NULL 2
5 2 0 2 2
6 3 0 3 3
7 4 0 2 2
8 4 0 2 2
9 4 0 2 2
10 4 0 2 2
11 4 1 NULL 4
12 11 0 2 2

Answer 3

I've added a VirtualParentOrgUnitId, which contains the parent with excluded nodes taken into account. I've also added a counter, VirtualDistance, which will report how many real hops there are between this node and it's virtual parent.
VirtualParentOrgUnitId will use the parent's ID if is not excluded, otherwise it will use it's parents's VirtualParentOrgUnitId, which allows chaining of multiple levels.
DROP TABLE IF EXISTS #OrgList
CREATE TABLE #OrgList (
OrgUnitId int,
ParentOrgUnitId int,
PersonId int,
isExcluded bit
);
INSERT INTO #OrgList(OrgUnitId, ParentOrgUnitId, PersonId, isExcluded) VALUES
(1, NULL, 100, 0), (2,1, 101, 0), (3,1,102,0), (4,2,103,1), (5,2,104,0), (6,3,105,0), (7,4,106,0), (8,4,107,0), (9,4,108,0), (10,4,109,0), (11,4,110,1), (12,11,111,0)
DROP TABLE IF EXISTS #Excludes
CREATE Table #Excludes (
OrgUnitId int
);
INSERT INTO #Excludes VALUES (4), (11);
with cte as (
select OrgUnitId, ParentOrgUnitId, ParentOrgUnitId VirtualParentOrgUnitId, 1 as VirtualDistance , PersonId, isExcluded , 0 as level_num
from #OrgList
where ParentOrgUnitId is null
UNION ALL
select o.OrgUnitId, o.ParentOrgUnitId, IIF(o.ParentOrgUnitId IN (SELECT OrgUnitId FROM #Excludes),cte.VirtualParentOrgUnitId, o.ParentOrgUnitId ), IIF(o.ParentOrgUnitId IN (SELECT OrgUnitId FROM #Excludes),VirtualDistance + 1, 1 ), o.PersonId, o.isExcluded , level_num+1 as level_num
from #OrgList o
join cte on o.ParentOrgUnitId=cte.OrgUnitId
)
select * from cte
Here are the results:
OrgUnitId ParentOrgUnitId VirtualParentOrgUnitId VirtualDistance PersonId isExcluded level_num
----------- --------------- ---------------------- --------------- ----------- ---------- -----------
1 NULL NULL 0 100 0 0
2 1 1 0 101 0 1
3 1 1 0 102 0 1
6 3 3 0 105 0 2
4 2 2 0 103 1 2
5 2 2 0 104 0 2
7 4 2 1 106 0 3
8 4 2 1 107 0 3
9 4 2 1 108 0 3
10 4 2 1 109 0 3
11 4 2 1 110 1 3
12 11 2 2 111 0 4

Answer 4

;
with cte as (
select OrgUnitId, ParentOrgUnitId, PersonId, isExcluded , 0 as level_num, 0 as level_after_exclusions,
cast(',' as varchar(max)) + case isExcluded when 1 then cast(OrgUnitId as varchar(20)) else '' end as excludedmembers,
case isExcluded when 1 then ParentOrgUnitId end as newParentId
from #OrgList
where ParentOrgUnitId is null
UNION ALL
select o.OrgUnitId, o.ParentOrgUnitId, o.PersonId, o.isExcluded , level_num + 1, level_after_exclusions + case o.isExcluded when 1 then 0 else 1 end,
excludedmembers + case o.isExcluded when 1 then cast(o.OrgUnitId as varchar(20))+',' else '' end,
case when excludedmembers like '%,'+cast(o.ParentOrgUnitId as varchar(20))+',%' then newParentId else o.ParentOrgUnitId end
from #OrgList o
join cte on o.ParentOrgUnitId=cte.OrgUnitId
)
select *, level_num - level_after_exclusions as shiftbylevels
from cte