案例陈述和除以零错误答案

【问题标题】：Case statement and divide by zero error案例陈述和除以零错误
【发布时间】：2013-05-21 16:05:17
【问题描述】：

我得到一个除以零的错误，我不知道如何处理它。使用 sql server 数据库。

脚本：

SELECT  Race ,
        [2012] = MAX(CASE WHEN a.[Year] = 2012 THEN [Count]
                     END) ,
        [% Inc Dec] = ( MAX(CAST(CASE WHEN a.[Year] IS NULL THEN ''
                        ELSE a.[Year] = 2011 THEN [Count]
                                 END AS FLOAT))
                        - MAX(CAST(CASE WHEN a.[Year] IS NULL THEN ''
                        ELSE a.[Year] = 2012 THEN [Count]
                                   END AS FLOAT)) )
        / MAX(CAST(CASE WHEN a.[Year] IS NULL THEN ''
                        ELSE a.[Year] = 2012 THEN [Count]
                   END AS FLOAT)) ,
        [2011] = MAX(CASE WHEN a.[Year] = 2011 THEN [Count]
                     END) ,
        [% Inc Dec] = ( MAX(CAST(CASE WHEN a.[Year] = 2010 THEN [Count]
                                 END AS FLOAT))
                        - MAX(CAST(CASE WHEN a.[Year] = 2011 THEN [Count]
                                   END AS FLOAT)) )
        / MAX(CAST(CASE WHEN a.[Year] = 2010 THEN [Count]
                   END AS FLOAT)) ,
        [2010] = MAX(CASE WHEN a.[Year] = 2010 THEN [Count]
                     END) ,
        [2009] = MAX(CASE WHEN a.[Year] = 2009 THEN [Count]
                     END) ,
        [% Inc Dec] = ( MAX(CAST(CASE WHEN a.[Year] = 2008 THEN [Count]
                                 END AS FLOAT))
                        - MAX(CAST(CASE WHEN a.[Year] = 2009 THEN [Count]
                                   END AS FLOAT)) )
        / MAX(CAST(CASE WHEN a.[Year] = 2009 THEN [Count]
                   END AS FLOAT)) 
FROM    @Data

我试图更改前两个 case 语句，但它不正确。任何帮助或推动正确的方向将不胜感激。

【问题讨论】：

CASE WHEN Denominator = 0 THEN 0
expression / NULLIF(Denominator,0) 将返回 NULL 而不是错误。
@data 中的数据是什么样的？只是种族、年份和计数列？还是 a.[year] 来自@data 之外的来源？我认为自联接可能是从 2 个不同行中减去值的更好方法，其中一行是第二年。

标签： sql sql-server case

【解决方案1】：

我假设a 是@Data 的别名，或者它与race 和[count] 在同一个表/源中，所以您的数据如下所示：

race    YEAR      COUNT
w       2012      10
w       2011      50
w       2010      100
b       2010      200
b       2009      75

并且您预计数据会随着时间的推移而减少。在减法和除法之前，我会使用自联接来确保高年和低年都有值，如下所示：

SELECT
 race, 
 y1.[YEAR] AS yr1, y1.[COUNT] AS cnt1, 
 y2.[YEAR] AS yr2, y2.[COUNT] AS cnt2, 
 (cnt2 - cnt1) / cnt1 AS pct_inc_dec
FROM 
 @DATA y1 INNER JOIN 
 @DATA y2 ON 
 y1.race = y2.race AND
 y1.YEAR = y2.YEAR - 1  -- y1 is the later year

那么你根本不用担心被零除，除非计数本身为零。

然后，使用您提供的代码，自联接将在交叉应用的枢轴之后应用于存储的表。您可以结合您上一年的标准，这样它就不必放在自己的表格中：

DECLARE @DATA TABLE
    (
      [YEAR] INT ,
      [COUNT] INT ,
      race VARCHAR(50)  
    )

INSERT  INTO @DATA
SELECT  
    Race ,[COUNT], [YEAR]
FROM    
            (SELECT  
                dt.YEAR AS YEAR ,
                SUM(ISNULL(caucasian_enrollment, 0)) AS caucasian ,
                SUM(ISNULL(black_or_african_american_enrollment, 0)) AS Black ,
                SUM(ISNULL(asian_enrollment,0)) AS Asian ,
                SUM(ISNULL(native_hawaiian_pacific_islander_enrollment, 0)) AS Native ,
                SUM(ISNULL(hispanic_enrollment, 0)) AS Hispanic ,
                SUM(ISNULL(american_indian_or_alaskan_ative_enrollment, 0)) AS [American Indian] ,
                SUM(ISNULL(multiracial_enrollment, 0)) AS multiracial ,
                SUM(ISNULL(unknown_ethnicity_enrollment, 0)) AS UNKNOWN ,
                SUM(ISNULL(male_enrollment, 0)) AS male,
                SUM(ISNULL(female_enrollment, 0)) AS female,
                SUM(ISNULL(Total_Enrollment, 0)) AS  [Total Enrollment]
            FROM    
                mart.dbo.f_s AS fes
                INNER JOIN TIME AS dt ON fes.time_key = dt.time_key
            WHERE   
                YEAR = '2012' 
            GROUP BY 
                dt.YEAR
        UNION ALL
            SELECT  
                dt.YEAR AS YEAR ,
                SUM(ISNULL(caucasian_enrollment, 0)) AS caucasian ,
                SUM(ISNULL(black_or_african_american_enrollment, 0)) AS Black ,
                SUM(ISNULL(asian_enrollment,0)) AS Asian ,
                SUM(ISNULL(native_hawaiian_pacific_islander_enrollment, 0)) AS Native,
                SUM(ISNULL(hispanic_enrollment, 0)) AS Hispanic,
                SUM(ISNULL(american_indian_or_alaskan_ative_enrollment, 0)) AS [American Indian] ,
                SUM(ISNULL(multiracial_enrollment, 0)) AS multiracial,
                SUM(ISNULL(unknown_ethnicity_enrollment, 0)) AS UNKNOWN,
                SUM(ISNULL(male_enrollment, 0)) AS male ,
                SUM(ISNULL(female_enrollment, 0)) AS female,
                SUM(ISNULL(Total_Enrollment, 0)) AS  [Total Enrollment]
            FROM    
                F5A_education_mart_IAK12.dbo.fact_enrollment_school AS fes
                INNER JOIN dim_time AS dt ON fes.time_key = dt.time_key
            WHERE   
                YEAR <= '2011' AND YEAR >= '2008'
            GROUP BY 
                dt.YEAR 
    ) d  CROSS APPLY 
    ( VALUES 
        ( 'Caucasian', caucasian, [YEAR])
        , ( 'Black', Black, [YEAR])
        , ( 'Asian', Asian, [YEAR]) 
        , ('Native', Native, [YEAR]) 
        , ('Hispanic', Hispanic, [YEAR]) 
        , ('American Indian', [American Indian], [YEAR]) 
        , ('Multiracial', multiracial, [YEAR])
        , ('Unkown', UNKNOWN, [YEAR]) 
        , ('Male', male, [YEAR]) 
        , ('Female', female, [YEAR]) 
        , ('Total Enrollment', [Total Enrollment], [YEAR]) 
        ) a ( Race, [COUNT], [YEAR] ) 
 GROUP BY 
    Race    

SELECT
    race, 
    y1.[YEAR] AS yr1, y1.[COUNT] AS cnt1, 
    y2.[YEAR] AS yr2, y2.[COUNT] AS cnt2, 
    (cnt2 - cnt1) / cnt1 AS pct_inc_dec
FROM 
    @DATA y1 INNER JOIN 
    @DATA y2 ON 
    y1.race = y2.race AND
    y1.YEAR = y2.YEAR - 1  -- y1 is the later year

【讨论】：

【解决方案2】：

感谢 T I 和 Martin 的快速响应。最初我没有发布完整的脚本，因为我只是对我的案例陈述有问题，我无法让 ISNULL 工作。以下是完整的结果和答案：

    DECLARE @Data TABLE
    (
      [Year] INT ,
      caucasian INT ,
      Black INT ,
      Asian INT ,
      Native INT ,
      Hispanic INT ,
      [American Indian] INT ,
      Multiracial INT ,
      UNKNOWN INT ,
      Male INT ,
      Female INT , 
      [Total Enrollment] INT 
    )

INSERT  INTO @Data
        SELECT  dt.year AS Year ,
                SUM(ISNULL(caucasian_enrollment, 0)) ,
                SUM(ISNULL(black_or_african_american_enrollment, 0)) ,
                SUM(ISNULL(asian_enrollment,0)) ,
                SUM(ISNULL(native_hawaiian_pacific_islander_enrollment, 0)) ,
                SUM(ISNULL(hispanic_enrollment, 0)) ,
                SUM(ISNULL(american_indian_or_alaskan_ative_enrollment, 0)) ,
                SUM(ISNULL(multiracial_enrollment, 0)) ,
                SUM(ISNULL(unknown_ethnicity_enrollment, 0)) ,
                SUM(ISNULL(male_enrollment, 0)) ,
                SUM(ISNULL(female_enrollment, 0)) ,
                SUM(ISNULL(Total_Enrollment, 0)) 
        FROM    mart.dbo.f_s AS fes
                INNER JOIN time AS dt ON fes.time_key = dt.time_key
                LEFT OUTER JOIN building AS db ON fes.building_key = db.building_key
        WHERE   year = '2012'
        GROUP BY dt.year
        UNION ALL
        SELECT  dt.year AS Year ,
                SUM(ISNULL(caucasian_enrollment, 0)) ,
                SUM(ISNULL(black_or_african_american_enrollment, 0)) ,
                SUM(ISNULL(asian_enrollment,0)) ,
                SUM(ISNULL(native_hawaiian_pacific_islander_enrollment, 0)) ,
                SUM(ISNULL(hispanic_enrollment, 0)) ,
                SUM(ISNULL(american_indian_or_alaskan_ative_enrollment, 0)) ,
                SUM(ISNULL(multiracial_enrollment, 0)) ,
                SUM(ISNULL(unknown_ethnicity_enrollment, 0)) ,
                SUM(ISNULL(male_enrollment, 0)) ,
                SUM(ISNULL(female_enrollment, 0)) ,
                SUM(ISNULL(Total_Enrollment, 0)) 
        FROM    F5A_education_mart_IAK12.dbo.fact_enrollment_school AS fes
                INNER JOIN dim_time AS dt ON fes.time_key = dt.time_key
                LEFT OUTER JOIN dim_building AS db ON fes.building_key = db.building_key
        WHERE   year = '2011'
        GROUP BY dt.year
        UNION ALL
        SELECT  dt.year AS Year ,
                SUM(ISNULL(caucasian_enrollment, 0)) ,
                SUM(ISNULL(black_or_african_american_enrollment, 0)) ,
                SUM(ISNULL(asian_enrollment,0)) ,
                SUM(ISNULL(native_hawaiian_pacific_islander_enrollment, 0)) ,
                SUM(ISNULL(hispanic_enrollment, 0)) ,
                SUM(ISNULL(american_indian_or_alaskan_ative_enrollment, 0)) ,
                SUM(ISNULL(multiracial_enrollment, 0)) ,
                SUM(ISNULL(unknown_ethnicity_enrollment, 0)) ,
                SUM(ISNULL(male_enrollment, 0)) ,
                SUM(ISNULL(female_enrollment, 0)) ,
                SUM(ISNULL(Total_Enrollment, 0)) 
        FROM    F5A_education_mart_IAK12.dbo.fact_enrollment_school AS fes
                INNER JOIN dim_time AS dt ON fes.time_key = dt.time_key
                LEFT OUTER JOIN dim_building AS db ON fes.building_key = db.building_key
        WHERE   year = '2010'
        GROUP BY dt.year
        UNION ALL
        SELECT  dt.year AS Year ,
                SUM(ISNULL(caucasian_enrollment, 0)) ,
                SUM(ISNULL(black_or_african_american_enrollment, 0)) ,
                SUM(ISNULL(asian_enrollment,0)) ,
                SUM(ISNULL(native_hawaiian_pacific_islander_enrollment, 0)) ,
                SUM(ISNULL(hispanic_enrollment, 0)) ,
                SUM(ISNULL(american_indian_or_alaskan_ative_enrollment, 0)) ,
                SUM(ISNULL(multiracial_enrollment, 0)) ,
                SUM(ISNULL(unknown_ethnicity_enrollment, 0)) ,
                SUM(ISNULL(male_enrollment, 0)) ,
                SUM(ISNULL(female_enrollment, 0)) ,
                SUM(ISNULL(Total_Enrollment, 0)) 
        FROM    F5A_education_mart_IAK12.dbo.fact_enrollment_school AS fes
                INNER JOIN dim_time AS dt ON fes.time_key = dt.time_key
                LEFT OUTER JOIN dim_building AS db ON fes.building_key = db.building_key
        WHERE   year = '2009'
        GROUP BY dt.year
        UNION ALL
        SELECT  dt.year AS Year ,
                SUM(ISNULL(caucasian_enrollment, 0)) ,
                SUM(ISNULL(black_or_african_american_enrollment, 0)) ,
                SUM(ISNULL(asian_enrollment,0)) ,
                SUM(ISNULL(native_hawaiian_pacific_islander_enrollment, 0)) ,
                SUM(ISNULL(hispanic_enrollment, 0)) ,
                SUM(ISNULL(american_indian_or_alaskan_ative_enrollment, 0)) ,
                SUM(ISNULL(multiracial_enrollment, 0)) ,
                SUM(ISNULL(unknown_ethnicity_enrollment, 0)) ,
                SUM(ISNULL(male_enrollment, 0)) ,
                SUM(ISNULL(female_enrollment, 0)) ,
                SUM(ISNULL(Total_Enrollment, 0)) 
        FROM    F5A_education_mart_IAK12.dbo.fact_enrollment_school AS fes
                INNER JOIN dim_time AS dt ON fes.time_key = dt.time_key
                LEFT OUTER JOIN dim_building AS db ON fes.building_key = db.building_key
        WHERE   year = '2008'
        GROUP BY dt.year 
--Race 2012 % inc/dec 2011 % inc/dec 2010
--Caucasian 3000 -.33 4000 .6 2500
--Black 1000 -.5 2000 .25 1500
--Asian 100 .5 50 .4 30

SELECT  Race ,
        [2012] = MAX(CASE WHEN a.[Year] = 2012 THEN [Count]
                     END) ,
        [% Inc Dec] = ( MAX(CAST(CASE WHEN a.[Year] = 2011 THEN [Count]
                                 END AS FLOAT))
                        - MAX(CAST(CASE WHEN a.[Year] = 2012 THEN [Count]
                    END AS FLOAT)) )
        / NULLIF(MAX(CAST(CASE WHEN a.[Year] = 2012 THEN [Count]
                   END AS FLOAT)),0) ,
        [2011] = MAX(CASE WHEN a.[Year] = 2011 THEN [Count]
                     END) ,
        [% Inc Dec] = ( MAX(CAST(CASE WHEN a.[Year] = 2010 THEN [Count]
                                 END AS FLOAT))
                        - MAX(CAST(CASE WHEN a.[Year] = 2011 THEN [Count]
                                   END AS FLOAT)) )
        / NULLIF(MAX(CAST(CASE WHEN a.[Year] = 2010 THEN [Count]
                   END AS FLOAT)),0) ,
        [2010] = MAX(CASE WHEN a.[Year] = 2010 THEN [Count]
                     END) ,
        [% Inc Dec] = ( MAX(CAST(CASE WHEN a.[Year] = 2009 THEN [Count]
                                 END AS FLOAT))
                        - MAX(CAST(CASE WHEN a.[Year] = 2010 THEN [Count]
                    END AS FLOAT)) )
        / NULLIF(MAX(CAST(CASE WHEN a.[Year] = 2009 THEN [Count]
                   END AS FLOAT)),0) ,
        [2009] = MAX(CASE WHEN a.[Year] = 2009 THEN [Count]
                     END) ,
        [% Inc Dec] = ( MAX(CAST(CASE WHEN a.[Year] = 2008 THEN [Count]
                                 END AS FLOAT))
                        - MAX(CAST(CASE WHEN a.[Year] = 2009 THEN [Count]
                                   END AS FLOAT)) )
        / NULLIF(MAX(CAST(CASE WHEN a.[Year] = 2009 THEN [Count]
                   END AS FLOAT)), 0)
FROM    @Data
        CROSS APPLY ( VALUES 
        ( 'Caucasian', caucasian, [Year])
        , ( 'Black', Black, [Year])
        , ( 'Asian', Asian, [Year]) 
        , ('Native', Native, [Year]) 
        , ('Hispanic', Hispanic, [Year]) 
        , ('American Indian', [American Indian], [Year]) 
        , ('Multiracial', multiracial, [Year])
        , ('Unkown', unknown, [Year]) 
        , ('Male', male, [Year]) 
        , ('Female', female, [Year]) 
        , ('Total Enrollment', [Total Enrollment], [Year]) 
        ) a ( Race, [Count], [Year] ) GROUP BY Race

【讨论】：