mysql - 左外加入 rails

Question

我有两个对象 - 客户和客户签到。每个客户有很多签到，每个签到属于一个客户。

我需要想出一个查询来输出完整的客户列表以及他们每月的签到次数。我当前的查询如下所示:

customer = Customer.where(account_id: 139).joins('LEFT JOIN
    customer_checkins on customer_checkins.customer_id =
    customers.id').uniq.select("COUNT(*) as count, customers.created_at as
    created_at, customers.name, customers.telephone, customers.mobile,
    customers.email, customers.gender, customers.city,
    customers.birthday,date_format(customer_checkins.created_at, '%b') as
    'month', customers.id").group("customer_checkins.customer_id,
    date_format(customer_checkins.created_at, '%b %Y')")

此查询未列出所有客户。我的代码有什么问题？

Answer 1

它不会列出所有客户，因为您只搜索 account_id 为 139 的客户。

替换

customer = Customer.where(account_id: 139)...

与

 customer = Customer...