Rails等效于SQL查询的活动记录查询

Question

如何为以下MySQL查询编写rails4活动记录等效查询？

SELECT c.id,c.account_name,sum(i.balance) as balance from clients c, invoices i 
where c.id = i.client_id GROUP BY  c.id

Answer 1

Client.joins(:invoices).select('clients.id, clients.account_name, sum(invoices.balance) as balance').group('clients.id')