Ruby on rails Rails：使用postgres防止被零除

我有一个带有postgre数据库的rails应用程序，我正试图通过以下语句获取一些指标

Negotiation.find(:all, :conditions => conditions_hash('negotiation'), :select => 'sum(payment_term * amount_after_annualised_base) / sum(amount_after_annualised_base) as pt').first

我如何确保总和（金额在年化基数之后）不是0（因此不会抛出“零除”错误）

我发现了这个，但不确定它是否正确/最佳/最有效

Negotiation.find(:all, :conditions => conditions_hash('negotiation'), :select => 'sum(payment_term * amount_after_annualised_base) / (CASE sum(amount_after_annualised_base) WHEN 0 THEN NULL ELSE sum(amount_after_annualised_base) END) as pt').first

谢谢！ 皮埃尔

怎么样：

Negotiation.find(:all, 
                 :conditions => conditions_hash('negotiation'), 
                 :select => 'sum(amount_after_annualised_base) sum_amount,
                             sum(payment_term * amount_after_annualised_base) / greatest(1,sum_amount) as pt').first

如果总和为零，请输入代码。

如何：

Negotiation.find(:all, 
                 :conditions => conditions_hash('negotiation'), 
                 :select => 'sum(amount_after_annualised_base) sum_amount,
                             sum(payment_term * amount_after_annualised_base) / greatest(1,sum_amount) as pt').first

如果总和为零，请输入代码。

使用：

这仅仅是您的解决方案的一个简写：

Negotiation.find(:all, :conditions => conditions_hash('negotiation'), :select => 'sum(payment_term * amount_after_annualised_base) / (CASE sum(amount_after_annualised_base) WHEN 0 THEN NULL ELSE sum(amount_after_annualised_base) END) as pt').first

使用：

这仅仅是您的解决方案的一个简写：

Negotiation.find(:all, :conditions => conditions_hash('negotiation'), :select => 'sum(payment_term * amount_after_annualised_base) / (CASE sum(amount_after_annualised_base) WHEN 0 THEN NULL ELSE sum(amount_after_annualised_base) END) as pt').first

---

我想你需要写一些类似的东西

Negotiation.find(
  :all, :conditions => conditions_hash('negotiation'), 
  :select => 'CASE sum(amount_after_annualised_base) WHEN 0 THEN NULL ELSE sum(payment_term * amount_after_annualised_base) / sum(amount_after_annualised_base) END as pt').first

---

如果

总和（年化基数后的金额）

为零，则返回NULL，否则将执行请求的除法。

我认为您需要编写以下内容

Negotiation.find(
  :all, :conditions => conditions_hash('negotiation'), 
  :select => 'CASE sum(amount_after_annualised_base) WHEN 0 THEN NULL ELSE sum(payment_term * amount_after_annualised_base) / sum(amount_after_annualised_base) END as pt').first

---

如果

总和（年化基数后的金额）

为零，则返回NULL，否则请求的除法无效。

这是否有效？因为你在任何情况下都会尝试除法，这样行吗？因为你在所有情况下都会尝试除法。很好，使用最大值（1，总和）是最酷的方法。谢谢。很好，使用最大的（1，总和）是最酷的方式。谢谢