Question

我有两张桌子;列表和出价。我想使用Ecto列出所有最高出价高于1且低于10的商品。有关架构和查询的更多信息，请参阅下面的代码。

数据库架构

listings
  id
  name


bids
  listing_id
  amount

program.ex

Repo.all(
  from l in Listing,
  where: (SELECT MAX(amount) FROM bids WHERE listing_id = l.id) > 1 and
         (SELECT MAX(amount) FROM bids WHERE listing_id = l.id) < 10)

怎么会这样呢？

Answer 1

作为group_by / having查询：

Repo.all(
  from l in Listing,
  join: b in assoc(l, :bids),
  group_by: l.id,
  having: (max(b.amount) > 1) and (max(b.amount) < 10)
  select: l)

Answer 2

Ecto.Query.API.fragment/1来救援：

join: l in Listing
where: fragment("
  ((SELECT MAX(amount) FROM bids WHERE listing_id = ?) > 1 and
   (SELECT MAX(amount) FROM bids WHERE listing_id = ?) < 10)
", l.id, l.id)

如何在Ecto中创建子查询？

2 个答案: