select a.userid,
       a.username,
       sum(b.incost) sumincost,
       sum(c.outcost) sumoutcost  
from xxzx_user_zyl a,xxzx_incost b, xxzx_outcost c
where a.userid=b.userid 
      and b.userid=c.userid  
group by a.userid,a.username

------解决方案--------------------
SQL code


SELECT userid,username,Sum(incost) over (PARTITION BY userid,username) as incost,Sum(outcost) over (PARTITION BY userid,username) as outcost FROM 
xxzx_user_zyl a,xxzx_incost b, xxzx_outcost c

WHERE a.userid=b.userid(+)
AND a.userid=c.userid(+)

------解决方案--------------------
select a.userid,        a.username,        sum(b.incost) sumincost,        sum(c.outcost) sumoutcost   from xxzx_user_zyl a,xxzx_incost b, xxzx_outcost c where a.userid=b.userid(+)        and A.userid=c.userid(+)   group by a.userid,a.username
是以A表为准,进行外关联