PIVOT on hierarchical data - sql

Question

I have a table like this:
Id Name parentId
--------------------------------
5 Rollers 2
2 Paint and Brushes 1
1 Decorating NULL
Using PIVOT or any other single query, can I get an output like this:
cat1id cat1name cat2id cat2name cat3id cat3Name
------------------------------------------------------------------------
1 Decorating 2 Paint and Brushes 5 Rollers

Answer 1

You can use PIVOT, UNPIVOT and a recursive query to perform this.
Static Version, is where you hard-code the values to the transformed:
;with hd (id, name, parentid, category)
as
(
select id, name, parentid, 1 as category
from yourtable
where parentid is null
union all
select t1.id, t1.name, t1.parentid, hd.category +1
from yourtable t1
inner join hd
on t1.parentid = hd.id
),
unpiv as
(
select value, 'cat_'+cast(category as varchar(5))+'_'+ col col_name
from
(
select cast(id as varchar(17)) id, name, parentid, category
from hd
) src
unpivot
(
value for col in (id, name)
) un
)
select [cat_1_id], [cat_1_name],
[cat_2_id], [cat_2_name],
[cat_3_id], [cat_3_name]
from unpiv
pivot
(
max(value)
for col_name in ([cat_1_id], [cat_1_name],
[cat_2_id], [cat_2_name],
[cat_3_id], [cat_3_name])
) piv
See SQL Fiddle with Demo
Dynamic Version, the values are generated at run-time:
;with hd (id, name, parentid, category)
as
(
select id, name, parentid, 1 as category
from yourtable
where parentid is null
union all
select t1.id, t1.name, t1.parentid, hd.category +1
from yourtable t1
inner join hd
on t1.parentid = hd.id
)
select category categoryNumber
into #temp
from hd
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + quotename('cat_'+cast(CATEGORYNUMBER as varchar(10))+'_'+col)
from #temp
cross apply (select 'id' col
union all
select 'name' col) src
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = ';with hd (id, name, parentid, category)
as
(
select id, name, parentid, 1 as category
from yourtable
where parentid is null
union all
select t1.id, t1.name, t1.parentid, hd.category +1
from yourtable t1
inner join hd
on t1.parentid = hd.id
),
unpiv as
(
select value, ''cat_''+cast(category as varchar(5))+''_''+ col col_name
from
(
select cast(id as varchar(17)) id, name, parentid, category
from hd
) src
unpivot
(
value for col in (id, name)
) un
)
select '+#cols+'
from unpiv
pivot
(
max(value)
for col_name in ('+#cols+')
) piv'
execute(#query)
drop table #temp
See SQL Fiddle with Demo
The Results are the same for both:
| CAT_1_ID | CAT_1_NAME | CAT_2_ID | CAT_2_NAME | CAT_3_ID | CAT_3_NAME |
--------------------------------------------------------------------------------
| 1 | Decorating | 2 | Paint and Brushes | 5 | Rollers |