特定のモデルに別モデルのカラムを別名で追加する方法 `SQL``Company` `belongs_to` `Balance``Backwardation` sql =<<-SQL SELECT balances.*, backwardations.rate FROM balances LEFT JOIN backwardations ON balances.date = backwardations.date AND balances.company_id = backwardations.company_id WHERE balances.company_id = #{company_id} SQL ActiveRecord::Base.connection.select_all(sql).to_hash `Hash``Balance``backwardation_rate` `AS` `Balance.select``FROM "balances"` `Balance``Backwardation``company_id``date``unique` DB`Postgresql`

`AS``ActiveRecord::Base.connection.select_all``Model.find_by_sql`


sql =<<-SQL
SELECT balances.*, backwardations.rate AS backwardations_rate
FROM balances LEFT JOIN backwardations
ON balances.date = backwardations.date AND balances.company_id = backwardations.company_id
WHERE balances.company_id = #{company_id}
SQL
balance = Balance.find_by_sql(sql)

balance.backwardations_rate #=> 0.5