mysql连接问题

Question

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)

Answer 1

这最多输出 3 个愿望(当他们没有愿望时，愿望列中为空)

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

---

不过，如果您不介意以逗号分隔的愿望列表，这可能会更好，而且更整洁:

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;

将输出:

name  |  wishes
------|----------------------
john  |  car,aircraft,bicycle
paul  |  motorbike,ipad