求sql代码，大佬求解答

Question

Answer 1

A表结构

B表结构

 

sql 实现 C表结构

select C.customtrade,group_concat(C.mid) from
(
select A.customtrade,
case when  LOCATE(B.customtrade,A.customtrade) >0 then id 
else '0' end mid
from A,B
) C where mid!=0 group by C.customtrade