SQL - 计算列类别

Question

我是 SQL 新手，但我正在尝试创建一个报告，我可以在其中计算学生购买的食物，并按种族/民族和每年的食物选择进行分类。

例如：

         2012                                          2013
Student Vegetarian     Meat           Unknown          Vegetarian     Meat           Unknown
---------------------------------------------------------------------------
Black    5 Purchases   4 Purchases      3 Purchases      5 Purchases   etc
White    4 Purchases   3 Purchases      3 Purchases      etc           etc
Asian    4 Purchases   1 Purchases      6 Purchases      etc           etc

虽然我能够在一个专栏中获得比赛，但我对不同食物类别的计数感到迷茫。我只知道 pur_type 被归类为“Veg”、“Me”和“Ukt”，分别代表 Vegetarian、Meat 和未知购买。

这是我尝试做的：

select 
     DATEPART(YYYY,pur_date) AS Year
    ,count (*) Citations
    , race
    , sex
    , ethnicity
    , GETDATE() as YTD
    ,COUNT(CASE WHEN pur_type = 'Veg' THEN 'Vegetarian' 
    WHEN pur_type = 'Me' THEN 'Meat' 
    WHEN pur_type  = 'UKt' THEN 'Unknown'  

         ELSE ''

         End as "Type"

, CASE 
    WHEN race='W' and sex='M' and ethnicity <> 'H' THEN 'Caucasian(Male)' 
    WHEN race='W' and sex='F' and ethnicity <> 'H' THEN 'Caucasian(Female)' 
    WHEN race='B' and sex='M' and ethnicity <> 'H' THEN 'African-American(Male)' 
    WHEN race='B' and sex='F' and ethnicity <> 'H' THEN 'African-American(Female)' 
    --WHEN race='A' and sex='M' and ethnicity <> 'H' THEN 'Pacific Islander(Male)' 
    --WHEN race='A' and sex='F' and ethnicity <> 'H' THEN 'Pacific Islander(Female)' 
    WHEN race='A' and sex='M' and ethnicity <> 'H' THEN 'Asian(Male)'  
    WHEN race='A' and sex='F' and ethnicity <> 'H' THEN 'Asian(Female)' 



    ELSE '' 
END as 'Race' 




from purchase
join purcharge
on purchase.purchaseid = purcharge.purchaseid
where pur_date between @startDate and  dateadd(DD, +1,  GETDATE())
and pur_type in ('Veg', 'Me', 'UKt')
GROUP BY DATEPART(YYYY,pur_date), race, sex, ethnicity , pur_type
ORDER BY 'Year','Race/Sex'

寻求指导。我想也许一个子查询会起作用，也许更多的案例陈述会起作用，但我无法计算每个种族的学生购买了多少食品类别。

另外，我正在尝试在 SSRS 报告中获取这些结果，因此它在 SQL 查询中可能看起来略有不同。

Answer 1

您可以查看PIVOT 语句，但如果是我，我会做更多的 CASE...WHEN 和 GROUP BY。

所以，而不是

COUNT(CASE WHEN pur_type = 'Veg' THEN 'Vegetarian' (etc) AS Type

我愿意

SUM(CASE WHEN pur_type = 'Veg' THEN 1 ELSE 0) AS Vegetarian

等等。

Answer 2

这并不是创建报告的最佳方式，但如果您需要使用 SQL（而不是使用另一层代码从一堆数据子集生成报告），您可以使用子查询。没有看到表结构，很难写查询，但可能是这样的：

Select
    race
    , (select count(*) from purchase where pur_type = 'Veg' and race = race) as Vegetables
    , (select count(*) from purchase where pur_type = 'Me' and race = race) as Meat
    , (select count(*) from purchase where pur_type = 'UKt' and race = race) as Unknown
From purchase

就像我说的，这并不理想，但它会为您提供不同的数据子集。

Answer 3

我不知道您的数据是什么样的，也没有时间构建示例数据，但我认为您实际上只是有一两个错字..

SELECT 
     DATEPART(YYYY,pur_date) AS [Year]
    ,count (*) Citations
    , race
    , sex
    , ethnicity
    , GETDATE() as YTD
    , COUNT(*) AS [PurchaseCount]
    , CASE 
        WHEN pur_type = 'Veg' THEN 'Vegetarian'
        WHEN pur_type = 'Me' THEN 'Meat'
        WHEN pur_type  = 'UKt' THEN 'Unknown'
        ELSE ''
    End as [Type]
, CASE 
    WHEN race='W' and sex='M' and ethnicity <> 'H' THEN 'Caucasian(Male)' 
    WHEN race='W' and sex='F' and ethnicity <> 'H' THEN 'Caucasian(Female)' 
    WHEN race='B' and sex='M' and ethnicity <> 'H' THEN 'African-American(Male)' 
    WHEN race='B' and sex='F' and ethnicity <> 'H' THEN 'African-American(Female)' 
    --WHEN race='A' and sex='M' and ethnicity <> 'H' THEN 'Pacific Islander(Male)' 
    --WHEN race='A' and sex='F' and ethnicity <> 'H' THEN 'Pacific Islander(Female)' 
    WHEN race='A' and sex='M' and ethnicity <> 'H' THEN 'Asian(Male)'  
    WHEN race='A' and sex='F' and ethnicity <> 'H' THEN 'Asian(Female)' 
    ELSE '' 
END as [Race] 
FROM purchase
JOIN purcharge
    ON purchase.purchaseid = purcharge.purchaseid
WHERE pur_date BETWEEN @startDate AND dateadd(DD, +1,  GETDATE())
    AND pur_type in ('Veg', 'Me', 'UKt')
GROUP BY DATEPART(YYYY,pur_date), race, sex, ethnicity , pur_type
ORDER BY [Year],[Race], [Type]

这不会准确给出您所要求的内容，因为它在您的 [Race] 案例陈述中包括种族和性别，但也许这就是您真正想要的，我不知道...

无论如何，我真正改变的只是 count(*) as [PurchaseCount] 、下一行的 CASE 语句和 GROUP BY 子句。 COUNT(*) 只会为您提供属于您的 GROUP BY 子句的记录数。在这种情况下，每个 [Year]、[Race] 和 [Type] 的记录计数