table a
-------------------------------------------------
id   name     wishlist1    wishlist2     wishlist3
1    john      1              2            3
2    paul      4              5
table b
--------------------------------------------------
id    goods
1     car
2     aircraft
3     bicycle
4     motorbike
5     ipad
result i want to get
---------------------------------------------------
john    car        aircraft    bicycle
paul    motorbike  ipad
 
我怎么能得到这个结果? (在mysql中)
最佳答案
这最多可输出3个愿望(如果没有愿望,则在愿望列中显示空值) 
select
  name,g1.goods as wish1,g2.goods as wish2,g3.goods as wish3
from tablea a
left join tableb g1.id on g1.wishlist1
left join tableb g2.id on g1.wishlist2
left join tableb g3.id on g1.wishlist3
 
这可能会更好,如果你不介意以逗号分隔的愿望清单,那就更好了: 
select
  name,group_concat(goods) as wishes
from tablea a
left join tableb b on b.id in (a.wishlist1,a.wishlist2,a.wishlist3)
group by name;
 
这将输出: 
name  |  wishes
------|----------------------
john  |  car,aircraft,bicycle
paul  |  motorbike,ipad
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