SQL表转换

Question

我有表A

customerID  Product
-------------------
 101            A
 101            B
 102            B
 102            C

想要将其转换为表格B，如：

customerID  ProductA ProductB ProductC
---------------------------------------
 101             1        1        0
 102             0        1        1  

我的最终目标是利用这个中间表来获得如下表C：

customerID   Product_Combo
--------------------------
 101              AB
 102              BC

我想我知道如何将它从B改为C.但是如何从A到B呢？谢谢！假设我们在MS SQL中执行此操作，并且我们只有三个产品A，B和C.

Answer 1

您可以将cursor用于customerId和此sql：

declare @Products varchar(10) = '';

--start cursor
set @Products = '';
SELECT @Products = @Products + [Product] 
  FROM [test].[dbo].[TableA]
  WHERE customerId = @cursor

print @Products
--end cursor

Answer 2

最简单的方法是使用案例：

q

结果

SELECT custId
,MAX(CASE WHEN product = 'A' THEN 1 ELSE 0 END) AS productA
,MAX(CASE WHEN product = 'B' THEN 1 ELSE 0 END) AS productB
,MAX(CASE WHEN product = 'C' THEN 1 ELSE 0 END) AS productC
 FROM A 
Group by  custId

Answer 3

你可以使用这样的查询进入B

SELECT
    CustomerId,
    CASE
        WHEN [A] = 'A' THEN 1
        ELSE 0
    END AS ProductA,
    CASE
        WHEN [B] = 'B' THEN 1
        ELSE 0
    END AS ProductB,
    CASE
        WHEN [C] = 'C' THEN 1
        ELSE 0
    END AS ProductC
FROM #tableA
PIVOT (MAX(Product) FOR Product IN ([A], [B], [C])) AS p