Способ перевести SQL запрос к Rails:
начальный запрос
select e.id, pt.name, nbc.nb
from `events` as e
inner join `executions` as ex on e.`execution_id` = ex.`id`
inner join `products` as p on ex.`product_id` = p.`id`
left outer join (select product_id, `name` from `product_translations` where `locale` ='en' group by `product_id` ) as pt on pt.`product_id` = p.id
left outer join (select event_id, COUNT(*) as nb from orders group by event_id) as nbc on nbc.event_id = e.id
where pt.name like '%plane%'
order by 3 desc
Первый шаг Определить основную таблицу; здесь, это Event
. Так что это звонок от вашей модели Event
.
Event
.select("events.id, pt.name, nbc.nb")
.joins("inner join `executions` as ex on events.`execution_id` = ex.`id`
inner join `products` as p on ex.`product_id` = p.`id`
left outer join (select product_id, `name` from `product_translations` where `locale` ='en' group by `product_id` ) as pt on pt.`product_id` = p.id
left outer join (select event_id, COUNT(*) as nb from orders group by event_id) as nbc on nbc.event_id = events.id")
.where("pt.name like '%plane%'")
.order("3 desc")
Второй шаг Transform внутреннее соединение в отношениях. Вы должны объявить has_many
/belongs_to
до Execution
и Product
.
Model Event < AR::Base
has_many :executions
has_many :products, :through => :executions
Event
.select("events.id, pt.name, nbc.nb")
.joins(:products)
.joins("left outer join (select product_id, `name` from `product_translations` where `locale` ='en' group by `product_id`) as pt on pt.`product_id` = products.id
left outer join (select event_id, COUNT(*) as nb from orders group by event_id) as nbc on nbc.event_id = events.id")
.where("pt.name like '%plane%'")
.order("3 desc")
подзапросов из Левых внешнего соединения не могут быть сделаны с Rails 4 в данный момент, но вы можете извлечь свои вложенные запросы.
sub_query1 = ProductTranslation
.select("product_id, `name`")
.where("`locale` ='en'")
.group("`product_id`")
sub_query2 = Order
.select("event_id, COUNT(*) as nb")
.group("event_id")
Event
.select("events.id, pt.name, nbc.nb")
.joins(:products)
.joins("left outer join (#{sub_query1.to_sql}) as pt on pt.`product_id` = products.id
left outer join (#{sub_query2.to_sql}) as nbc on nbc.event_id = events.id")
.where("pt.name like '%plane%'")
.order("3 desc")
Некоторые другие поправляет команды SQL являются Upcase, условия хэш, предпочитают использовать table_name для моделей таблицы.
sub_query1 = ProductTranslation
.select("`product_id`, `name`")
.where({ :locale => 'en' })
.group(:product_id)
sub_query2 = Order
.select("event_id, COUNT(*) as nb")
.group("event_id")
Event
.select("#{Event.table_name}.id, pt.name, nbc.nb")
.joins(:products)
.joins("LEFT OUTER JOIN (#{sub_query1.to_sql}) AS pt
ON pt.`product_id` = #{Product.table_name}.id
LEFT OUTER JOIN (#{sub_query2.to_sql}) AS nbc
ON nbc.event_id = #{Event.table_name}.id")
.where("pt.name LIKE ?", '%plane%')
.order("3 DESC")
Voilà!
Проблема заключается в том, что у меня нет модели ProductTranslation, потому что она управляется Gemlizeize. –