Flatten table rows into columns in SQL Server [duplicate]

Answer 1

I would use conditional aggregate along with row_number():

select code,
       max(case when seqnum = 1 then code end) as code_1,
       max(case when seqnum = 2 then code end) as code_2,
       max(case when seqnum = 3 then code end) as code_3
from (select t.*,
             row_number() over (partition by code order by data) as seqnum
      from t
     ) t
group by code;