Rails的：防止被零除在Postgres

我有我的軌道與postgre數據庫應用程序，我試圖得到一些指標，用下面的語句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

我怎麼能確保總和（amount_after_annualised_base ）不是0（因此不會拋出「除零」錯誤）？

我發現了這個，但不知道它是正確的/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

謝謝！皮埃爾

來源

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

這僅僅是你的解決方案consise速記：

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

來源

2011-03-01 13:55:38

這是行不通的？因爲你仍然試圖在所有情況下進行分工。 – nathanvda 2011-03-01 14:12:36

它實際上工作。爲了簡明起見，我拿這個 – 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

，並在你的代碼檢查，如果sum_amount爲零。

來源

2011-03-01 12:34:48

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

我認爲你需要寫類似

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

這將返回如果sum(amount_after_annualised_base)爲零，則爲NULL，否則請求的divis離子。

來源

2011-03-01 14:11:24 nathanvda

Rails的：防止被零除在Postgres

回答

相關問題