如何在 SQL 数据库中创建层次结构？

Question

I have a table with the following columns:

I need to create more columns based on the number of levels and based on the hierarchy.

For example:

Level 1
Architecture ->Level 2
             ->Asses Inventory ->level 3
                              ->Program

I need create three columns if there are a maximum of three levels. I have achieved this in PowerBI.

How can I achieve the same thing in SQL? Any help is appreciated. Thanks

Answer 1

In T-SQL I'd just join the table to itself multiple times

Create a new table how you want it then something like:

   INSERT INTO NEW_TABLE
(LEVEL1, LEVEL2, LEVEL3)
SELECT
a.name,
b.name,
c.name
FROM TABLE1 a
LEFT OUTER JOIN TABLE1 b
ON a.category_id = b.parent_id
LEFT OUTER JOIN TABLE1 c
on b.category_id = c.parent_id
GO

That should do what you're after I think.

Answer 2

You can use hierarchyid type. It comes with a lot of methods to work with the hierarchy itself like:

• GetAncestor
• GetDescendant
• GetLevel
• GetRoot
• IsDescendantOf

In your example, you will have something like this:

ID      Name
/1/     Architecture
/1/1/   Asses Invenctory
/1/2/   Process2
/2/     Assset Management