Pivot Table issue: no identifier in original table or enumeration - sql

Question

I'm having an issue with using pivot or dynamic tables.
I found this example to be very helpful in understanding how I can accomplish this task; however, I am missing the inside identifier column.
Dynamic Pivot Columns in SQL Server
There is an SQL fiddle provided here in the post above: http://www.sqlfiddle.com/#!3/7fad2/6
You can see that in the second table propertyObjects, there is a count 1, 2, 3, 4 for each objectID. I do not have that propertyID count. This is all I have
case category
1 xx
1 xyx
1 abc
2 ghj
2 asdf
3 dfgh
As you can see I have a number of different categories for each case, but no category identifier field.
This is what I need:
case cat1 cat2 cat3
1 xx xyx abc
2 ghj asdf
3 dfgh
So I am thinking I might need to add a column to the source table and somehow enumerate the categories per case. This would make it possible for me to use the pivot in the provided example. Thoughts?
I tried to use row_number to accomplish this, but it does not stop at each case number, it just continues on counting the entire table.

Answer 1

Since you have multiple values for each case, then you will need to use row_number() to get the separate columns for each category.
Before you write the dynamic SQL version I would first write a hard-coded version. The code will be similar to:
SELECT [case], cat1, cat2, cat3
FROM
(
SELECT [case], category,
'cat'+
cast(row_number() over(partition by [case]
order by category) as varchar(10)) seq
FROM yourTable
) x
PIVOT
(
max(category)
for seq in (cat1, cat2, cat3)
)p;
See SQL Fiddle with Demo.
Now you have the logic down, then you can convert it to dynamic SQL:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + QUOTENAME('cat'+cast(seq as varchar(10)))
from
(
select row_number() over(partition by [case]
order by category) seq
from yourtable
) d
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT [case],' + #cols + '
from
(
SELECT [case], category,
''cat''+
cast(row_number() over(partition by [case]
order by category) as varchar(10)) seq
FROM yourTable
) x
pivot
(
max(category)
for seq in (' + #cols + ')
) p '
execute sp_executesql #query;
See SQL Fiddle with Demo. This will give you the result:
| CASE | CAT1 | CAT2 | CAT3 |
|------|------|--------|--------|
| 1 | abc | xx | xyx |
| 2 | asdf | ghj | (null) |
| 3 | dfgh | (null) | (null) |