3、行列转换（列转行）

解题思路：

先按dt, result分组，然后用case when把列转成行，最后sum起来。

select
  dt,
  sum(case when result='win' then cnt else 0 end) as win,
  sum(case when result='loss' then cnt else 0 end) as loss
from (
select dt, result,count(1) as cnt from info group by 1,2
);