Pivot table with custom values - sql-server

Question

i have table say FIDDLE HERE
+----+------+------+-----+-----+
| id | year | sell | buy | own |
+----+------+------+-----+-----+
| 1 | 2016 | 9 | 2 | 10 |
| 1 | 2017 | 9 | | 10 |
| 1 | 2018 | | 2 | 10 |
| 2 | 2016 | 7 | 2 | 11 |
| 2 | 2017 | 2 | | |
| 2 | 2018 | | | 18 |
+----+------+------+-----+-----+
create table test(id varchar(20), year varchar(20),
sell varchar(20), buy varchar(20),
own varchar(20));
insert into test values('1', '2016','9','2','10' )
insert into test values('1', '2017','9',NULL,'10' )
insert into test values('1', '2018',NULL,'2','10' )
insert into test values('2', '2016','7','2','11' )
insert into test values('2', '2017','2',NULL,'17' )
insert into test values('2', '2018','5','2','18' )
I'm trying to PIVOT but instead of aggregate the values, i wanted to keep some letters if it is not null (S-Sell,B-Buy,O-Own). If there are values for all columns for particular year then i need S_B_O for that year. If there are values only for sell and buy then S_B etc., so Expected output is
+----+-------+------+------+
| ID | 2016 | 2017 | 2018 |
+----+-------+------+------+
| 1 | S_B_O | S_O | B_O |
+----+-------+------+------+
| 2 | S_B_O | S | O |
+----+-------+------+------+
The closest i have got is using conditional aggrgarion( MAX and concat) instead of PIVOT but this is also giving null if any one is NULL. Please suggest a solution.
select ID,
MAX(CASE WHEN Year = '2016' AND sell is not null THEN 'S_' END +
CASE WHEN Year = '2016' AND buy is not null THEN 'B_' END +
CASE WHEN Year = '2016' AND own is not null THEN 'O' END)
AS [2016],
MAX(CASE WHEN Year = '2017' AND sell is not null THEN 'S_' END +
CASE WHEN Year = '2017' AND buy is not null THEN 'B_' END +
CASE WHEN Year = '2017' AND own is not null THEN 'O' END)
AS [2017]
/* ......for all year */
from test
group by id
FIDDLE HERE

Answer 1

You can use CONCAT function, which will handle NULLs automatically.
select ID,
CONCAT(MAX(CASE WHEN Year = '2016' AND sell is not null THEN 'S_' END) ,
MAX(CASE WHEN Year = '2016' AND buy is not null THEN 'B_' END) ,
MAX(CASE WHEN Year = '2016' AND buy is not null THEN 'O' END))
AS [2016],
CONCAT(MAX(CASE WHEN Year = '2017' AND sell is not null THEN 'S_' END) ,
MAX(CASE WHEN Year = '2017' AND buy is not null THEN 'B_' END) ,
MAX(CASE WHEN Year = '2017' AND buy is not null THEN 'O' END))
AS [2017]
from test
group by id
+----+-------+------+
| ID | 2016 | 2017 |
+----+-------+------+
| 1 | S_B_O | S_ |
| 2 | S_B_O | S_ |
+----+-------+------+
UPDATE Dynamic query. As #Larnu told, You should have asked this as separate question. You should not change the requirement.
DECLARE #lst_Years NVARCHAR(MAX) , #query NVARCHAR(MAX)
SET #lst_Years = STUFF((SELECT distinct ',' + QUOTENAME([Year])
FROM test
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
SET #query = 'SELECT * FROM
(
select ID, [Year],
CONCAT(MAX(CASE WHEN sell is not null THEN ''S_'' END) ,
MAX(CASE WHEN buy is not null THEN ''B_'' END) ,
MAX(CASE WHEN buy is not null THEN ''O'' END))
AS [Value]
from test
group by id, [year]) as t
pivot
(
max(value) FOR YEAR IN (' + #lst_Years + ')
) as pvt'
EXEC(#query)
+----+-------+------+-------+
| ID | 2016 | 2017 | 2018 |
+----+-------+------+-------+
| 1 | S_B_O | S_ | B_O |
| 2 | S_B_O | S_ | S_B_O |
+----+-------+------+-------+