sql - 如何在Rails中的联接表上指定条件

我试图用ActiveRecord在Rails中进行查询，该查询在连接的表上指定了一些条件。即使我遵循此处的示例，我似乎也无法使其正常工作:

http://guides.rubyonrails.org/active_record_querying.html#specifying-conditions-on-the-joined-tables

从guides:



我的数据库架构如下所示，带有表scores，submissions和tasks:

  create_table "scores", :force => true do |t|
    t.integer  "value"
    t.integer  "user_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  add_index "scores", ["user_id"], :name => "index_scores_on_user_id"

  create_table "submissions", :force => true do |t|
    t.integer  "user_id"
    t.integer  "task_id"
    t.integer  "score_id"
    t.datetime "completed_at"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  add_index "submissions", ["score_id"], :name => "index_submissions_on_score_id"
  add_index "submissions", ["task_id"], :name => "index_submissions_on_task_id"
  add_index "submissions", ["user_id"], :name => "index_submissions_on_user_id"

  create_table "tasks", :force => true do |t|
    t.integer  "episode_id"
    t.integer  "score"
    t.string   "key"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

所以我想做一个查询，在这里我可以找到与特殊任务有关的所有“分数”。提交属于任务和分数。

我的查询现在看起来像这样:

Score.joins(:submission).where(:submission => {:task_id => 1})

这将生成以下语法:

SELECT "scores".* FROM "scores" INNER JOIN "submissions" ON "submissions"."score_id" = "scores"."id" WHERE "submission"."task_id" = 1

会产生以下错误:

SQLite3::SQLException: no such column: submission.task_id

但是有一列submission.task_id，您可以在数据库模式中看到它。我可以成功做到这一点:

SELECT "submissions".* FROM "submissions" WHERE "submissions"."task_id" = 1

最佳答案

子句中的名称应为复数形式以引用表名称:

Score.joins(:submission).where(:submissions => {:task_id => 1})