mysql - sql query problem

Question

There are two tables (only used to represent structures)

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

I want to get data like name-----sum(num)
Please give me some advice

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