如何将多个 table 与多个 where 连接起来

Question

我的目的是获取所有与 school_admin 或 dormitory_admin

有关系的用户

所以这是 tables。

users (has one school_admin or has one dormitory_admin)
-id
-username

has_one :school_admin
has_one :dormitory_admin

school_admins (pivot table)
-id
-school_id
-user_id

belongs_to :user
belongs_to :school

dormitory_admins (pivot table)
-id
-dormitory_id
-user_id

school (has many dormitory)
-id
-name

has_many :dormitories

dormitory (belongs to one school)
-id
-school_id

这是我当前的查询（我现在有 2 个查询，我需要将它们合并为一个查询）

@q1 = User.joins(:school_admin).where(school_admin: { school_id: current_user.school_admin.school_id }).select("users.id, users.username, school_admin.name, school_admin.phone").ransack(params[:q])
@q2 = User.joins(:dormitory_admin).where(dormitory_admin: { dormitory_id: current_user.school_admin.school.dormitories.pluck(:id) }).select("users.id, users.username, dormitory_admin.name, dormitory_admin.phone").ransack(params[:q])

我正在使用 ransack gem 进行 table 过滤，并使用 PostgreSQL 进行数据库处理。

我可以像 ActiveRecord::Base.connection.execute(sql) 一样使用纯 SQL 来执行“UNION”，但是如果我使用它，搜查 gem 将不起作用。

Answer 1

您可以在现有范围上使用 to_sql，然后将其粘贴到 from 子句中

 query1 =  User.joins(:school_admin).where(school_admin: current_user.school_admin).select("users.id, users.username, school_admins.name, school_admins.phone")
    
 query2 = User.joins(:dormitory_admin).where(dormitory_admin: current_user.dormitory_admin).select("users.id, users.username, dormitory_admins.name, dormitory_admins.phone")
    
    
 User.from("(#{query1.to_sql} UNION #{query2.to_sql}) AS users").ransack(params[:q])
    
    
    SELECT "users".* FROM (
        SELECT 
        users.id, 
        users.username, 
        school_admins.name, 
        school_admins.phone 
        FROM "users" 
        INNER JOIN "school_admins" 
        ON "school_admins"."user_id" = "users"."id" 
        WHERE "users"."id" = 1 
        UNION 
        SELECT 
        users.id, 
        users.username, 
        dormitory_admins.name, 
        dormitory_admins.phone 
        FROM "users" 
        INNER JOIN "dormitory_admins" 
        ON "dormitory_admins"."user_id" = "users"."id" 
        WHERE "users"."id" = 2) 
    AS users;

或者更好的方法是避免重复查询

User.from("(#{User.joins(:school_admin).where(school_admin: current_user.school_admin).select("users.id, users.username, school_admins.name, school_admins.phone").to_sql} UNION #{User.joins(:dormitory_admin).where(dormitory_admin: current_user.dormitory_admin).select("users.id, users.username, dormitory_admins.name, dormitory_admins.phone").to_sql}) AS users").ransack(params[:q])

注：我用的table名字是复数school_admins& dormitory_admins。另外，我修改了 query1 & query2

中的 where 子句

如何将多个 table 与多个 where 连接起来

How to join multiple table with multiple where

ruby

postgresql

ruby-on-rails

ruby-on-rails-6