建议你提供详细的资料：
例如表的结构，表之间的关系，测试数据，相关算法及需要的结果。
这样有助于我们理解你的意思，更主要的是能尽快让你获得答案或解决问题的方法。

------解决方案--------------------

SQL code
select m.tradeDay , m.Amount + isnull(n.Amount,0) from
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) m
left join
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) n
on m.tradeDay = n.tradeDay

然后判断拿最大的日期及最大的值出来
select max(tradeDay) , max(Amount) from
(
select m.tradeDay , m.Amount + isnull(n.Amount,0) Amount from
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) m
left join
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) n
on m.tradeDay = n.tradeDay
) t

最大的日期所在的记录
select m.tradeDay , m.Amount + isnull(n.Amount,0) Amount from
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) m
left join
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) n
on m.tradeDay = n.tradeDay
order by m.tradeDay desc

最大的值出来所在的记录
select m.tradeDay , m.Amount + isnull(n.Amount,0) from
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) m
left join
(select convert(varchar(10),tradeDay,120) tradeDay, sum(Amount) Amount from tb group by convert(varchar(10),tradeDay,120)) n
on m.tradeDay = n.tradeDay
order by Amount desc