Question

我在params [：医院]中列出了两家医院的键值选择，我试图在下面的查询中使用params [：hospital]编写一个条件来条件行。

params[:hospitals].each do |hospital, xyz|
      <!--code -->
     Condition.find_by_hospital_id(Hospital.find_by_hospital_name(hospital).id)//query

Params包含

{"utf8"=>"✓",
 "authenticity_token"=>"",
 "client"=>{"Client1"=>"1"},
 "hospital"=>{"hospital1"=>"Client1", "hospital2" => "client2"},
 "type"=>"BOTH",
 "beg-dt-tm"=>"",
 "datepicker"=>"",
 "end-dt-tm"=>"",
 "controller"=>"",
 "action"=>""}

我的问题：是否有更好的方法通过避免多次调用表来编写查询

由于

Answer 1

如果医院有很多条件：

class Hospital < ActiveRecord::Base
  has_many :conditions
end

然后你应该能够在一个查询中加载所有内容：

hospitals = Hospital.where(hospital_name: params[:hospitals]).includes(:conditions)

hospitals.each do |hospital|
  # no further SQL queries will be run, because the conditions have been preloaded
  hospital.conditions.each do |condition|
    # do something with this condition
  end
end

Answer 2

只需进行两次查询。首先按名字加载所有医院，第二个加载所有医院条件。看起来应该是这样的：

hospitals = Hospital.where(hospital_name: params[:hospitals])
conditions = Condition.where(hospital_id: hospitals)

在这种情况下，只会执行两次DB查询。

避免对rails中的表进行多次查询

2 个答案: