Question

我有一个范围：

includes(:countries).where("profiles.sector = :sector OR advices.sector = :sector", :sector => sector)

它产生以下SQL：

SELECT `profiles`.* FROM `profiles` INNER JOIN `advices` ON `advices`.`profile_id` = `profiles`.`id` WHERE (profiles.sector = 'Forestry_paper' OR advices.sector = 'Forestry_paper')

（是的，我的Profile和Country型号中有国家/地区

不幸的是，OR似乎失败了：

它不会呈现仅具有适当扇区但没有相关建议的配置文件。想法？

Answer 1

您正在进行INNER JOIN，因此需要配置文件具有相应的建议。请尝试以下方法：

Profile
  .joins("LEFT JOIN advices ON advices.profile_id = profiles.id")
  .where("profiles.sector = :sector OR advices.sector = :sector", :sector => sector)

这还包括没有建议的配置文件。

Answer 2

您可以通过在includes：

之后指定带有哈希的where子句来执行外连接

Post.includes(:comments).where(:comments=>{:user_id=>nil})

产生

  Post Load (0.5ms)  SELECT "posts"."id" AS t0_r0, "posts"."created_at" AS t0_r1,
   "posts"."updated_at" AS t0_r2, "comments"."id" AS t1_r0, "comments"."user_id" 
   AS t1_r1, "comments"."post_id" AS t1_r2, "comments"."content" AS t1_r3,
   "comments"."created_at" AS t1_r4, "comments"."updated_at" AS t1_r5 
   FROM "posts" LEFT OUTER JOIN "comments" ON "comments"."post_id" = "posts"."id" 
   WHERE ("comments"."user_id" IS NULL)

Ryan Bigg写了helpful blog post about this。

修改

请注意，这种技术或多或少是Rails为急切加载关联构造SQL的方式的副作用。如接受的答案所示，显式LEFT JOIN更加健壮。

Answer 3

~~查看http://metautonomo.us/projects/metawhere/以获得更多查询优势......~~

meta_where现在没有维护：https://github.com/activerecord-hackery/meta_where

Rails 5引入了OR语句： Rails 5: ActiveRecord OR query

Rails，范围，OR和连接

3 个答案: