How update a table column as per hierarchy in SQL

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SQL-Server-2014

Hi I have data as below and we are assuming parent node where Id=Parent_Id, so there are three top parents(1,5,7).

Id	Parent_Id	Title
1	1	Parent1
2	1	
3	2	
5	5	Parent2
6	5	
7	7	Parent3
8	7	
9	8

I want to update result to all descendants of parent node and the result should be as below.

Id	Parent_Id	Title
1	1	Parent1
2	1	Parent1
3	2	Parent1
5	5	Parent2
6	5	Parent2
7	7	Parent3
8	7	Parent3
9	8	Parent3

What I have tried:

I am able to update parent to it's immediate child, so i am unable to update tile of level 3.

Please suggest how to proceed.

Posted 5-Mar-19 23:42pm

Mohd Wasif

Updated 6-Mar-19 0:48am

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MadMyche · Answer 1 · 2019-03-06T00:49:00

Your "level 3" items are not immediate children of the parent, so they will not update with the query.

Id	Parent_Id	Title
1	1	Parent1
2	1	// Child of 1 (Parent1)
3	2	// Child of 2, grandchild of 1 (Parent1)
5	5	Parent2
6	5	// Child of 5 (Parent2)
7	7	Parent3
8	7	// Child of 7 (Parent3)
9	8	// Child of 8, grandchild of 7 (Parent3)

You will need to run a second query for the grandchildren to match the parents, something like this should get you started

SQL

UPDATE t1
SET    t1.Title = t2.Title
FROM   HierarchyTable    t1
INNER JOIN HierarchTable t2 ON t1.Parent_Id = t2.Id