SELECT a.uid, a.idate,a.step, a.eatcalory,a.actcalory,b.isj,b.isc FROM  

ta a left join  tb b on a.uid = b.uid where a.uid =845444

union 

SELECT a.uid, a.idate,a.step, a.eatcalory,a.actcalory,b.isj,b.isc FROM  

ta a right join  tb b on a.uid = b.uid where a.uid =845444

------解决方案--------------------
 (不要高估你的汉语表达能力或者我的汉语理解能力)
  建议你列出你的表结构，并提供测试数据以及基于这些测试数据的所对应正确结果。
  参考一下这个贴子的提问方式http://topic.csdn.net/u/20091130/20/8343ee6a-417c-4c2d-9415-fa46604a00cf.html
   
  1. 你的 create table xxx .. 语句
  2. 你的 insert into xxx ... 语句
  3. 结果是什么样，（并给以简单的算法描述）
  4. 你用的数据库名称和版本(经常有人在MS SQL server版问 MySQL)
   
  这样想帮你的人可以直接搭建和你相同的环境，并在给出方案前进行测试，避免文字描述理解上的误差。



------解决方案--------------------
SQL code
select 
  isnull(a.uid,b.uid) as uid,
  isnull(a.idate,b.idate) as idate,
  isnull(a.step,0) as step,
  isnull(a.eatcalory,0) as eatcalory,
  isnull(a.actcalory,0) as actcalory,
  isnull(b.isj,0) as isj,
  isnull(b.isc,0) as isc
from a
full join b on a.uid=b.uid and a.idate=b.idate

------解决方案--------------------
select uid,idate,step,sum(eatcalory),sum(actcalory),sum(isj),sum( isc)
form (
select uid,idate,step,eatcalory,actcalory,0 as isj,0 as isc
from a
union all
select uid,idate,0,0,0, isj, isc
from b
) t
group by uid,idate