Rails的：防止被零除在Postgres

我有我的轨道与postgre数据库应用程序，我试图得到一些指标，用下面的语句Rails的：防止被零除在Postgres

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

我怎么能确保总和（amount_after_annualised_base ）不是0（因此不会抛出“除零”错误）？

我发现了这个，但不知道它是正确的/最好的/最有效的方式。

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

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2011-03-01 Pierre

使用nullif：

Negotiation.find(:all, :conditions => conditions_hash('negotiation'), :select => 'sum(payment_term * amount_after_annualised_base)/nullif(sum(amount_after_annualised_base),0) as pt').first

这仅仅是你的解决方案consise速记：

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

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2011-03-01 13:55:38

这是行不通的？因为你仍然试图在所有情况下进行分工。 – nathanvda 2011-03-01 14:12:36

它实际上工作。为了简明起见，我拿这个 – Pierre 2011-03-01 18:52:36

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

，并在你的代码检查，如果sum_amount为零。

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2011-03-01 12:34:48

不错，使用最大（1，sum_amount）是最酷的方式。谢谢。 – Fred 2013-04-09 15:58:36

我认为你需要写类似

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

这将返回如果sum(amount_after_annualised_base)为零，则为NULL，否则请求的divis离子。

来源

2011-03-01 14:11:24 nathanvda

Rails的：防止被零除在Postgres

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