将MS Access计数和数据透视查询转换为SQL Server

Question

我有杂货店数据库。 我想计算收据上每个类别有多少产品。

表是：

• Transactions （id_transaction，数量，id_receipt，id_product）
• Receipts （id_receipt，日期，id_store，id_customer）
• Products （id_product，product_name，price，id_prod_cat）
• Product_Categories类别（id_prod_cat，类别名称）

所需的输出与样本数据：

ID_RECEIPT |   desserts | meat |   juices | baker products| canned |
-------------------------------------------------------------------|
1          |   0        |   2  |    1     |     3         |   0    |
2          |   1        |   0  |    3     |     1         |   0    |
--------------------------------------------------------------------

我已经尝试过此查询，但没有成功。

TRANSFORM Nz(Count(dbo.Transactions.quantity), 0) AS Product Count 
SELECT dbo.Receipts.id_receipt 
FROM dbo.Product_Categories 
INNER JOIN (dbo.Receipts 
   INNER JOIN (dbo.PRODUCTS 
      INNER JOIN dbo.TRANSACTIONS ON dbo.PRODUCTS.id_product = dbo.TRANSACTIONS.id_product) 
      ON dbo.RECEIPTS.id_receipt = dbo.TRANSACTIONS.id_receipt)  
   ON dbo.Product_Categories.id_prod_cut = dbo.Products.id_product 
GROUP BY 
    dbo.Receipts.id_receipt 
PIVOT 
    dbo.Product_Categories.category_name

Answer 1

本质上，这是经典的转置查询。 考虑以下应与大多数RDMS兼容的SQL。 对于MS Access，您将使用IIF()而不是CASE WHEN （和联接中的括号）。 使用Transform的交叉表查询主要是MS Access类型，而Pivot()主要是SQL Server函数。 但是，以下内容应可跨数据库方言使用。

SELECT 
    dbo.Receipts.id_receipt,
    Count(CASE WHEN dbo.Product_Categories.category_name='desserts' 
               THEN dbo.Transactions.quantity END) As [desserts],
    Count(CASE WHEN dbo.Product_Categories.category_name='meat' 
               THEN dbo.Transactions.quantity END) As [meat],
    Count(CASE WHEN dbo.Product_Categories.category_name='juices' 
               THEN dbo.Transactions.quantity END) As [juices],
    Count(CASE WHEN dbo.Product_Categories.category_name='baker products' 
               THEN dbo.Transactions.quantity END) As [baker products],
    Count(CASE WHEN dbo.Product_Categories.category_name='canned' 
               THEN dbo.Transactions.quantity END) As [canned]

FROM dbo.Product_Categories
INNER JOIN dbo.Receipts 
INNER JOIN dbo.PRODUCTS 
INNER JOIN dbo.TRANSACTIONS ON dbo.PRODUCTS.id_product = dbo.TRANSACTIONS.id_product 
     ON dbo.RECEIPTS.id_receipt = dbo.TRANSACTIONS.id_receipt
     ON dbo.Product_Categories.id_prod_cut = dbo.Products.id_product 

GROUP BY dbo.Receipts.id_receipt ;