create table B(id int, uid varchar(10), sj datetime,je decimal(18,2))
insert into b values(1 ,'张三', '2012-02-01', 200.00)
insert into b values(2 ,'李四', '2012-02-01', 100.00)
insert into b values(4 ,'张三', '2012-02-15', 100.00)
create table C(id int, uid varchar(10), sj datetime,je decimal(18,2))
insert into c values(1 ,'张三', '2012-02-02', 200.00)
insert into c values(2 ,'赵六', '2012-02-05', 100.00)
insert into c values(3 ,'陈七', '2012-02-17', 50.00)
go

select isnull(m.uid,n.uid) uid ,
       isnull(m.je , 0) 充值金额,
       isnull(n.je , 0) 消费金额,
       isnull(m.je , 0) - isnull(n.je , 0) 余额
from
(select uid , sum(je) je from b where convert(varchar(10),sj,120) between '2012-02-01' and '2012-02-15' group by uid) m
full join
(select uid , sum(je) je from c where convert(varchar(10),sj,120) between '2012-02-01' and '2012-02-15' group by uid) n
on m.uid = n.uid

drop table b , c

/*
uid        充值金额                                     消费金额                                     余额                                       
---------- ---------------------------------------- ---------------------------------------- ---------------------------------------- 
李四         100.00                                   .00                                      100.00
张三         300.00                                   200.00                                   100.00
赵六         .00                                      100.00                                   -100.00

（所影响的行数为 3 行）
*/