Question

我有三个模型Table1，Table2和Table1to2。 Table1to2是Table1到Table2的连接表，Table1和Table2的模式为：

schema "table1" do
  many_to_many :table2, Table2, join_through: Table1to2
end 

schema "table2" do
  many_to_many :table1, Table1, join_through: Table1to2
end

关键是我的联接表Table1to2有一个我需要查询的列/字段。基本上，我想做这样的事情：

Repo.get!(Table1, id) |> Repo.preload(table2: (from j in Table1to2, where: [main: true]))

这是可行的，因为从Table1到Table1to2没有直接定义的关联。但是这样做：

Repo.get!(Table1, id) |> Repo.preload(table2: (from j in Table2, where: [main: true]))

导致此查询：

from p0 in Table1,
  join: u in Table1to2,
  on: u.table1_id == p0.id,
  join: p1 in Table2,
  on: u.table2_id == p1.id,
  where: p1.main == true,        #should be u.main == true
  where: p0.id == ^"2",
  select: p0,
  preload: [table_2: p1]

Answer 1

您始终可以使用查询语法，例如您发布的结果查询，以满足您的需求。

query = 
  from t1 in Table1,
  join: t12 in Table1to2, on: t12.table1_id == t1.id,
  join: t2 in Table2, on: t12.table2_id == t2.id,
  where: t12.main == :true and t1.id == ^table1_id,
  preload: [table2: t1],
  select: t1

result = Repo.one(query)

在ecto assoc join表上添加where子句

1 个答案: