SQL 除以零误差

Question

我有一个恼人的问题，它阻止我生成一些数据； SQL作业一共23步，21日失败。

-- Step 21 Create the table z1QReportOverview
-- Create z1QReportProjectOverview.sql
-- Project Overview - By Category (Part 4).sql
USE database
SELECT z1QReportProjectOverview1.[ERA Category] AS Category,
z1QReportProjectOverview1.[Total Projects Signed],
z1QReportProjectOverview1.[Total Spend Under Review],
z1QReportProjectOverview1.[Avg. Project Size],
z1QReportProjectOverview2.[Work in Progress],
z1QReportProjectOverview2.[Implemented],
z1QReportProjectOverview2.[No Savings],
z1QReportProjectOverview2.[Lost],
CONVERT(decimal(18,0),[Lost])/CONVERT(decimal(18,0),[Total Projects Signed]) AS [Loss Ratio],
z1QReportProjectOverview2.[Completed],
(
    CONVERT(decimal(18,0),([Completed]+[Implemented]))/
    CONVERT(decimal(18,0),([Completed]+[Implemented]+[Lost]))
) 
AS [Success Ratio],
z1QReportProjectOverview3.[Avg. Spend] AS [Average Spend],
z1QReportProjectOverview3.[Avg. Savings] AS [Average Savings],
z1QReportProjectOverview3.[Avg. Savings %] AS [Average Savings %]
INTO dbo.z1QReportProjectOverview
FROM dbo.z1QReportProjectOverview1
JOIN dbo.z1QReportProjectOverview2
ON (z1QReportProjectOverview1.[ERA Category] = z1QReportProjectOverview2.[ERA    Category])
JOIN dbo.z1QReportProjectOverview3
ON (z1QReportProjectOverview2.[ERA Category] = z1QReportProjectOverview3.[ERA     Category])
ORDER BY Category

我相信我知道导致被零除错误的原因。

'Lost' 字段由三个字段组成，在某些情况下（非常罕见）所有 3 个字段均为 0，导致 'Lost' 字段中为 0。

我相信这是错误的主要原因，但那里也有第二个部门，我在 SQL 很垃圾所以我的问题：

CASE WHEN 子句应该放在哪里？

-很可能也写错了:( "CASE When [Lost] = 0 SET [Total Projects Signed] = 0"

非常感谢任何建议！

Answer 1

您可以使用CASE来检查分度值是否为0。

CASE WHEN CONVERT(decimal(18,0),[Lost]) <> 0 THEN 
        CONVERT(decimal(18,0),[Lost])/CONVERT(decimal(18,0),[Total Projects Signed]) 
     ELSE 0 END AS [Loss Ratio],
z1QReportProjectOverview2.[Completed],
CASE WHEN CONVERT(decimal(18,0),([Completed]+[Implemented]+[Lost])) <> 0 THEN 
      (CONVERT(decimal(18,0),([Completed]+[Implemented]))/CONVERT(decimal(18,0),([Completed]+[Implemented]+[Lost]))) 
    ELSE 0 END AS [Success Ratio],

Answer 2

您可以像这样使用 CASE WHEN：

CASE 
     -- check if either value is 0 (which will cause error)
     WHEN CONVERT(decimal(18,0),[Lost]) = 0
       OR CONVERT(decimal(18,0),[Total Projects Signed]) = 0
     -- if so, return 0
     THEN 0
     -- otherwise perform calculation
     ELSE CONVERT(decimal(18,0),[Lost])/CONVERT(decimal(18,0),[Total Projects Signed])
END AS [Loss Ratio]

Answer 3

使用NULLIF处理被零除错误

........
Isnull(CONVERT(DECIMAL(18, 0), [Lost]) / NULLIF(CONVERT(DECIMAL(18, 0), [Total Projects Signed]), 0), 0) AS [Loss Ratio],
Isnull(CONVERT(DECIMAL(18, 0), ( [Completed] + [Implemented] )) /
                        NULLIF(CONVERT(DECIMAL(18, 0), ( [Completed] + [Implemented] + [Lost] )), 0), 0) AS [Success Ratio], 
........

Answer 4

@坦纳：

所以像这样布置代码应该没问题吧？

CONVERT(decimal(18,0),[Lost])/CONVERT(decimal(18,0),[Total Projects Signed]) AS [Loss Ratio],
CASE 
 -- check if either value is 0 (which will cause error)
 WHEN CONVERT(decimal(18,0),[Lost]) = 0
   OR CONVERT(decimal(18,0),[Total Projects Signed]) = 0
 -- if so, return 0
 THEN 0
 -- otherwise perform calculation
ELSE CONVERT(decimal(18,0),[Lost])/CONVERT(decimal(18,0),[Total Projects Signed])
END AS [Loss Ratio]
z1QReportProjectOverview2.[Completed],
(
    CONVERT(decimal(18,0),([Completed]+[Implemented]))/
    CONVERT(decimal(18,0),([Completed]+[Implemented]+[Lost]))
) 
AS [Success Ratio],

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