如何从MySQL中没有任何关系的两个表中获取记录？

Question

我有两张桌子。

表1（abc）包含这些列

 ____________________________
|__id__|__userid__|__points__|
|__1__ |_____2____|____30____|
|__2__ |_____2____|____50____|
|__3__ |_____3___ |____40____|

表2（xyz）

 ________________________________
|__id__|__userid__|__usedpoints__|
|__1__ |_____2____|______10______|
|__2__ |_____3____|______20______|
|__3__ |_____2___ |______15______|

如何从这两个表中获取这样的记录？

 _________________________________________
|__userid__|__totalpoints__|__usedpoints__|
|____2____ |_______80______|______25______|
|____3____ |_______40______|______20______|

Answer 1

select u1.userid, sum(u1.points) as totalpoints, u2.usedpoints
from table1 u1
left join 
(
   select userid, sum(usedpoints) as usedpoints
   from table2
   group by userid
) u2 on u1.userid = u2.userid
group by u1.userid  

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