ActiveRecord where 选择查询结果的条件答案

【问题标题】：ActiveRecord where condtion on selected query resultActiveRecord where 选择查询结果的条件
【发布时间】：2018-06-18 03:24:05
【问题描述】：

Borrower.joins("INNER JOIN receivables ON receivables.borrower_id = borrowers.id")
.where("borrowers.type='moulde_b'")
.select(" borrowers.id as id,sum(receivables.amount) as invoice_amount");

从上面的结果集中，我试图在 select 语句之后执行 where 条件。

我正在尝试类似下面的方法，

Borrower.joins("INNER JOIN receivables ON receivables.borrower_id = borrowers.id")
    .where("borrowers.type='moulde_b'")
    .select(" borrowers.id as id,sum(receivables.amount) as invoice_amount").where("receivables.amount = 12323.23");

在 SUM 列上选择 where 条件后真的可以这样做吗？

【问题讨论】：

标签： mysql ruby-on-rails ruby ruby-on-rails-4 activerecord

【解决方案1】：

使用ActiveRecord::QueryMethods#having 代替where：

Borrower.
  joins("INNER JOIN receivables ON receivables.borrower_id = borrowers.id").
  where("borrowers.type = 'moulde_b'").
  select("borrowers.id as id, sum(receivables.amount) as invoice_amount").
  group("borrowers.id"). # mandatory for having
  having("invoice_amount = 12323.33")

链接这些方法的顺序并不重要，因为AR 会在构建真正的 SQL 查询时重新排列它。

【讨论】：