Table transformation logic in SQL - sql

Question

I have a table T :
CREATE TABLE T
(
id INT,
type VARCHAR(200),
type_value VARCHAR(10),
value VARCHAR(200)
);
INSERT INTO T VALUES (1, 'RoomColor', 'room1', 'yellow');
INSERT INTO T VALUES (1, 'RoomColor', 'room2', 'red');
INSERT INTO T VALUES (2, 'RoomColor', 'room1', 'blue');
INSERT INTO T VALUES (2, 'RoomColor', 'room1', 'pink');
INSERT INTO T VALUES (3, 'RoomColor', 'room1', 'white');
INSERT INTO T VALUES (3, 'RoomColor', 'room2', 'grey');
INSERT INTO T VALUES (3, 'RoomColor', 'room2', 'brown');
INSERT INTO T VALUES (4, 'RoomColor', 'room3', 'green');
I need to transform it into :
id BedRoomColor DiningRoomColor
-------------------------------------------
1 yellow red
2 blue pink
3 white grey
4 green null
Logic behind the transformation:
If there are more than two room type_value then discard the third room type_value
For same id if there are more than one room type_value ( for example room1,room1 or room2,room2 or room1,room2) then use first type_value to create as BedRoomColor and second type_value to create DiningRoomColor
If there is only 1 room type_value (for eg. room1 or room2 or room3) for an id then corresponding value ( red,green,yellow etc ) will be placed in BedRoomColor and DiningRoomColor will be null
I am struggling with this logic for couple of days. Can anyone please help me.
Thanks

Answer 1

You can use this script
;WITH CTE AS (
SELECT *, RN = ROW_NUMBER() OVER(PARTITION BY id ORDER BY type_value) FROM T
)
SELECT id, [1] BedRoomColor, [2] DiningRoomColor FROM
(SELECT id,value, RN FROM CTE ) SRC
PIVOT (MAX(value) FOR RN IN ([1], [2]) ) AS PVT
Result:
id BedRoomColor DiningRoomColor
----------- ------------------ ---------------
1 yellow red
2 blue pink
3 white grey
4 green NULL

Answer 2

Another way and with adding type to query is:
;with tt as (
select *,
row_number() over (partition by [type], id order by type_value) rn
-- ^^^^^^ I add type to support other types if there is
from t
)
select id,
max(case when [type] = 'RoomColor' and rn = 1 then [value] end) 'BedRoomColor',
max(case when [type] = 'RoomColor' and rn = 2 then [value] end) 'DiningRoomColor'
from tt
group by id;
SQL Server Fiddle Demo

Answer 3

try this:
with tmp as (
select T.*, rownumber() over(patition by id order by type_value) rang
from T
)
select f1.id, f1.value as BedRoomColor, f2.value as DiningRoomColor
from tmp f1
left outer join tmp f2 on f1.id=f2.id and f2.rang=2
where f1.rang=1