从两个不同的表计算增长百分比时除以零误差

Posted 2023-03-24

【中文标题】从两个不同的表计算增长百分比时除以零误差

【英文标题】：division by zero error while calculating growth percentage from two different tables

【发布时间】：2020-09-12 22:10:20

【问题描述】：

我目前拥有的表是这样的：（数据来自两个不同的表，19921231、19930331）

我要创建的表如下所示（添加了第 5 列）

目标：确定每家银行的存款增长率。 IE。比较上一季度在银行持有的存款（例如 19921231）与最近一个季度的存款（例如 19930331）。然后以百分比的形式查看增加/减少。

这是我目前写的代码：

select 
AL.repdte as `Date`, AL.cert, AL.name, AL.dep as `Deposits`
FROM usa_fdic_call_reports_1992.All_Reports_19921231_Assets_and_Liabilities as AL

UNION ALL

select 
AL.repdte as `Date`, AL.cert, AL.name, AL.dep as `Deposits`
FROM usa_fdic_call_reports_1993.All_Reports_19930331_Assets_and_Liabilities as AL

An answer to this question 建议使用此代码，但由于某种原因，我得到了“NULL”的输出

select al19930331.repdte as `Date`, al19930331.cert, al19930331.name,
       al19930331.dep as Deposits_1993,
       al19921231.dep as Deposits_1992,
       (al19930331.dep - al19921231.dep) / al19921231.dep as grow_rate
from usa_fdic_call_reports_1993.All_Reports_19930331_Assets_and_Liabilities as al19930331 left join
     usa_fdic_call_reports_1992.All_Reports_19921231_Assets_and_Liabilities as al19921231
     on al19930331.cert = al19921231.cert and
        al19930331.name = al19921231.name and
        al19921231.repdte = date_add(al19930331.repdte, interval 1 year);

为了隔离“NULL”问题，我能够消除“NULL”问题。我通过简单地查询来做到这一点。它很有效，我能够查看两个季度的“存款”。

select al19930331.repdte as `Date`, al19930331.cert, al19930331.name,
       al19930331.dep as Deposits_1993,
       al19921231.dep as Deposits_1992,
       (al19930331.dep - al19921231.dep) / al19921231.dep as grow_rate
from usa_fdic_call_reports_1993.All_Reports_19930331_Assets_and_Liabilities as al19930331 left join
     usa_fdic_call_reports_1992.All_Reports_19921231_Assets_and_Liabilities as al19921231
     on al19930331.cert = al19921231.cert and
        al19930331.name = al19921231.name

一旦我确定检索过去两个季度的存款数据似乎没有任何问题，我决定删除这段代码的最后一行：

select al19930331.repdte as `Date`, al19930331.cert, al19930331.name,
       al19930331.dep as Deposits_1993,
       al19921231.dep as Deposits_1992,
       (al19930331.dep - al19921231.dep) / al19921231.dep as grow_rate
from usa_fdic_call_reports_1993.All_Reports_19930331_Assets_and_Liabilities as al19930331 left join
     usa_fdic_call_reports_1992.All_Reports_19921231_Assets_and_Liabilities as al19921231
     on al19930331.cert = al19921231.cert and
        al19930331.name = al19921231.name and
        al19921231.repdte = date_add(al19930331.repdte, interval 1 year);

到这里：

select al19930331.repdte as `Date`, al19930331.cert, al19930331.name,
       al19930331.dep as Deposits_1993,
       al19921231.dep as Deposits_1992,
       (al19930331.dep - al19921231.dep) / al19921231.dep as grow_rate
from usa_fdic_call_reports_1993.All_Reports_19930331_Assets_and_Liabilities as al19930331 left join
     usa_fdic_call_reports_1992.All_Reports_19921231_Assets_and_Liabilities as al19921231
     on al19930331.cert = al19921231.cert and
        al19930331.name = al19921231.name

这有点工作，但是它暴露了一个“被零除”的错误。所以现在的问题是如何添加一个解决方案来消除错误除法，这将使我能够添加最后一行代码？

【参考方案1】：

要修复除零错误，您可以进行安全除法。 BigQuery 有一个功能：

   IEEE_DIVIDE((al19930331.dep - al19921231.dep), al19921231.dep) as grow_rate

不过，我倾向于使用NULLIF()，这是一个标准的SQL函数：

   (al19930331.dep - al19921231.dep) / NULLIF(al19921231.dep, 0) as grow_rate

【讨论】：

成功了。谢谢戈登。仅供参考：使用最后一行时我无法获得有效查询：al19921231.repdte = date_add(al19930331.repdte, interval 1 year);它在三列中的两列上返回 Null。