SQL Rows to Separate Columns - sql

Question

I realise this maybe similar to other questions, but I am stuck!
I am having trouble organising some data into an appropriate format to export to another tool. Basically I have an ID column and then 2 response columns. I would like to separate the ID and then list the responses under each. See the example below for clarification.
I have played around with Pivot and UnPivot but can't get it quite right.
Here is how the data looks now.
ID X1 X2
1 2 Y
1 5 Y
1 3 N
1 7 N
1 6 Y
2 5 N
2 4 Y
2 8 Y
2 3 N
3 5 Y
3 1 N
3 9 N
Here is how I would like the data to look
ID1_X1 ID1_X2 ID2_X1 ID2_X2 ID3_X1 ID3_X2
2 Y 5 N 5 Y
5 Y 4 Y 1 N
3 N 8 Y 9 N
7 N 3 N null null
6 Y null null null null
Here is the code to create/populate the table.
create table #test (ID int, X1 int, X2 varchar(1))
insert into #test values
('1','2','Y'),('1','5','Y'),('1','3','N'),('1','7','N'),
('1','6','Y'),('2','5','N'),('2','4','Y'),('2','8','Y'),
('2','3','N'),('3','5','Y'),('3','1','N'),('3','9','N')

Answer 1

You can do this using aggregation and row_number() . . . assuming you know the ids in advance:
select max(case when id = 1 then x1 end) as x1_1,
max(case when id = 1 then x2 end) as x2_1,
max(case when id = 2 then x1 end) as x1_2,
max(case when id = 2 then x2 end) as x2_2,
max(case when id = 3 then x1 end) as x1_3,
max(case when id = 3 then x2 end) as x2_3
from (select t.*,
row_number() over (partition by id order by (select null)) a seqnum
from #test t
) t
group by seqnum;
I should note that SQL tables represent unordered sets. Your original data doesn't have an indication of the ordering, so this is not guaranteed to put the values in the same order as the original data (actually, there is no such order that that statement is a tautology). If you have another column with the ordering, then you can use that.

Answer 2

Here is a alternative approach to Gordan's good answer using OUTER JOIN's
Considering that there is a Identity column in your table to define the order of X1 in each ID and fixed number of ID's
;WITH FST
AS (SELECT ROW_NUMBER()OVER(ORDER BY IDENTITY_COL) RN,X1 AS ID1_X1,X2 AS ID1_X2
FROM #TEST A
WHERE ID = 1),
SCD
AS (SELECT ROW_NUMBER()OVER(ORDER BY IDENTITY_COL) RN,X1 AS ID2_X1,X2 AS ID2_X2
FROM #TEST A
WHERE ID = 2),
TRD
AS (SELECT ROW_NUMBER()OVER(ORDER BY IDENTITY_COL) RN,X1 AS ID3_X1,X2 AS ID3_X2
FROM #TEST A
WHERE ID = 3)
SELECT ID1_X1,ID1_X2,ID2_X1,ID2_X2,ID3_X1,ID3_X2
FROM FST A
FULL OUTER JOIN SCD B
ON A.RN = B.RN
FULL OUTER JOIN TRD C
ON C.RN = COALESCE(B.RN, A.RN)