我想编写一个查找程序查询，该查询返回具有计划的所有成员对象，而该计划的ID是“ 1”，“ 2”或“ 3”。我怎么做？我尝试编写一个查找程序，仅查找ID“ 1”，但在评估时出现此错误...

Question

[8] pry(main)> Member.where(:plans => {:associate => {:id => "1"}}).count
   (0.7ms)  SELECT COUNT(*) FROM "Members" WHERE "associate"."id" IS NULL
ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "associate"
LINE 1: SELECT COUNT(*) FROM "members" WHERE "associate"."id" ...
                                              ^
: SELECT COUNT(*) FROM "members" WHERE "associate"."id" IS NULL
from /Users/davea/.rvm/gems/ruby-2.5.1/gems/activerecord-5.2.2.1/lib/active_record/connection_adapters/postgresql_adapter.rb:611:in `async_exec'

我正在使用Rails 5.1。我有以下模型...类Member ：nullify class Plan

您必须首先使用joins创建一个INNER JOIN查询。之后，您可以访问联接表：