SQL服务器：如何只对部分语法进行分组

Question

我在创建 SQL 服务器查询时遇到问题。

总而言之，查询应该得到 sum 和 count 的列，按 customerID 分组，另一列按未用作 grouper 列的列分组。

我的问题是只对部分语法进行分组，而列不需要分组的情况。

样本数据，测试：

customerID, 1,2,3,4...
InvoiceID, 1234551, 1234552...
ProductID, A, B, C...
Date, Datetime
Income, int

customerID	InvoiceID	ProductID	Date	Income
1	1234551	A	01/01/2015	300
2	1234552	B	02/01/2016	300

我有一个解决方案，但我确信还有一个更简单的解决方案。

SELECT DISTINCT 
    Test.CustomerId,
    ISNULL(TBL.Income_2015, 0) AS Income_2015,
    ISNULL(TBL_2.Income_2016, 0) AS Income_2016,
    CASE 
        WHEN Test.ProductID = 'A' 
            THEN 'TRUE' 
            ELSE 'FALSE' 
    END AS 'purchase_product_A',
    TBL_3.Invoices
FROM
    Test
LEFT OUTER JOIN 
    (SELECT CustomerId, SUM(Income) AS Income_2015 
     FROM Test 
     WHERE YEAR(Date) = 2015 
     GROUP BY CustomerId) TBL ON Test.customerID = TBL.customerID
LEFT OUTER JOIN
    (SELECT CustomerId, SUM(Income) AS Income_2016 
     FROM Test 
     WHERE YEAR(Date) = 2016 
     GROUP BY CustomerId) TBL_2 ON Test.customerID = TBL_2.customerID
LEFT OUTER JOIN
    (SELECT CustomerId, COUNT(InvoiceID) AS Invoices 
     FROM Test 
     GROUP BY CustomerId) TBL_3 ON Test.customerID = TBL_3.customerID

生产：

customerID, 1,2,3...
Income_2015, int
Income_2016, int
Invoices, int
Purchase_product_A, boolean

customerID	Income_2015	Income_2016	Invoices	Purchase_product_A
1	300	300	2	TRUE
10	0	400	1	FALSE

谢谢！尼尔

Answer 1

您可以对单次查询使用条件聚合：

SELECT
    CustomerId,
    SUM(CASE WHEN YEAR(Date) = 2015 THEN Income ELSE 0 END) AS Income_2015,
    SUM(CASE WHEN YEAR(Date) = 2016 THEN Income ELSE 0 END) AS Income_2016,
    COUNT(InvoiceID) AS Invoices,
    CASE WHEN COUNT(CASE WHEN ProductID = 'A' THEN 1 END) > 0
         THEN 'TRUE' ELSE 'FALSE' END AS [Purchase_product_A]
FROM Test
GROUP BY
    CustomerId;

SQL服务器：如何只对部分语法进行分组

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