sql 查询问题

Question

有两张表 (只是用来表示结构)

1. name code
   1 --------1
   1 --------2
   1 --------3
   2----------5
   2----------4
   2.
   code num
   1-------2
   2 ------ 3
   3------ 4
   4-------5
   5--------6

我想 获得name-----sum(num) 这样的数据
求大神 提点

Answer 1

select name,sum(num) from A inner join B on A.code =B.code group by name

Answer 2

SELECT SUM(num) FROM 2 WHERE code IN (SELECT code FROM 1 WHERE name = 1)

Answer 3

select 2.num from 1 inner join 2 2 on 2.code=1.code