Question

I have the following Location table

ID  Name       ParentID
-----------------------
1   TopLevel   NULL
2   Region 1   1
3   Fleet 1    2
4   Fleet 2    2

I have just recently finished up writing a recursive CTE to display this structure in a hierarchy approach:

TopLevel
-Region 1
--Fleet 1
--Fleet 2

I now need to write a query to return this structure in a column hierarchal format:

Level1     Level2   Level3  Level4  Level5  Level6
Top Level
Top Level  Region 1 Fleet 1
Top Level  REgion 1 Fleet 2

The maximum levels deep a location can go is 9. How would I accomplish this? I was trying to use the recursive CTE and build on that, but I don’t think that is going to work. Any other ideas?

Answer 1

Here would be one method to accomplish the output, using a recursive CTE hard-coded to fill out up to 9 levels worth of hierarchy (you would need to change table/column references as necessary to your real object names, and you may need to increase varchar(50) if the actual type of name column is wider than that):

with cte as (
  select id, 1 as level,
    name as level1,
    cast(null as varchar(50)) as level2,
    cast(null as varchar(50)) as level3,
    cast(null as varchar(50)) as level4,
    cast(null as varchar(50)) as level5,
    cast(null as varchar(50)) as level6,
    cast(null as varchar(50)) as level7,
    cast(null as varchar(50)) as level8,
    cast(null as varchar(50)) as level9
  from table1 t
  where parentid is null

  union all

  select t.id, cte.level + 1 as level,
    case when level = 0 then t.name else cte.level1 end as level1,
    case when level = 1 then t.name else cte.level2 end as level2,
    case when level = 2 then t.name else cte.level3 end as level3,
    case when level = 3 then t.name else cte.level4 end as level4,
    case when level = 4 then t.name else cte.level5 end as level5,
    case when level = 5 then t.name else cte.level6 end as level6,
    case when level = 6 then t.name else cte.level7 end as level7,
    case when level = 7 then t.name else cte.level8 end as level8,
    case when level = 8 then t.name else cte.level9 end as level9
  from table1 t
  inner join cte on cte.id = t.parentid
)
select * from cte;

Sample Output:

| ID | LEVEL |   LEVEL1 |   LEVEL2 |  LEVEL3 | LEVEL4 | LEVEL5 | LEVEL6 | LEVEL7 | LEVEL8 | LEVEL9 |
----------------------------------------------------------------------------------------------------
|  1 |     1 | TopLevel |   (null) |  (null) | (null) | (null) | (null) | (null) | (null) | (null) |
|  2 |     2 | TopLevel | Region 1 |  (null) | (null) | (null) | (null) | (null) | (null) | (null) |
|  3 |     3 | TopLevel | Region 1 | Fleet 1 | (null) | (null) | (null) | (null) | (null) | (null) |
|  4 |     3 | TopLevel | Region 1 | Fleet 2 | (null) | (null) | (null) | (null) | (null) | (null) |

Demo: http://www.sqlfiddle.com/#!6/0bd5d/14