如果知道原始列，可以执行以下操作：

select c.col1,
       sum(case when to = 'A' then weight else 0 end) as a,
       sum(case when to = 'B' then weight else 0 end) as b,
       sum(case when to = 'C' then weight else 0 end) as c,
       sum(case when to = 'D' then weight else 0 end) as d,
       sum(case when to = 'E' then weight else 0 end) as d
from (select 'A' as col1 union all select 'B' union all select 'C' union all select 'D' union all select 'E'
     ) c left join
     t
     on t.from = c.col1
group by c.col1;

如果不知道原始列，可以将这些值组合成单个字符串：

select col1.col, 
       group_concat(col2.col, ':', t.weight order by col2.col)
from ((select `from` as col from t
      ) union   -- on purpose to remove duplicates
      (select `to` from t
      )
     ) col1 cross join
     ((select `from` as col from t
      ) union   -- on purpose to remove duplicates
      (select `to` from t
      )
     ) col2 left join
     t
     on col1.col = t.`from` and col2.col = t.`from`
group by col1.col;

如果您确实需要单独的列，并且不知道这些值，那么您将需要动态sql。