SQL Server - 获取TOP 1产品的总计数

Question

我需要能够找到客户下达的订单总数,还可以在一个查询中找到最佳产品.例如,在以下结构中,

CREATE TABLE #Cust (CustId INT, CustName VARCHAR(50))
CREATE TABLE #Product (ProductId INT, ProductName VARCHAR(10) )
CREATE TABLE #Orders (CustId INT, ProductId INT, OrderTaken BIT)

INSERT #Cust
        ( CustId, CustName )
VALUES  ( 1, 'Paul' ),
        ( 2, 'F' ),
        ( 3, 'Francis' )

INSERT #Product
        ( ProductId, ProductName )
VALUES  ( 1, 'Table' ),
        ( 2, 'Chair' )

INSERT #Orders
        ( CustId, ProductId, OrderTaken )
VALUES  ( 1, 1, 1 ),
        ( 1, 1, 1 ),
        ( 1, 2, 1 ),
        ( 2, 1, 1 )

我想出了一个问题,

SELECT * FROM #Cust AS C OUTER APPLY 
( 
    SELECT TOP 1 SQ.ProductId, SUM(SQ.TotalCount) AS TotalQty FROM 
    (
        SELECT O.ProductId, COUNT(*) TotalCount 
        FROM #Orders AS O WHERE O.CustId = C.CustId 
        GROUP BY O.CustId , O.ProductId
    ) SQ 
    GROUP BY SQ.ProductId 
) X

但是,这并没有给我我想要的结果,因为Paul给了我正确的ProductId,但仅仅是那个产品的数量.

我想要一个Query返回,

CustId  |   CustName    |   ProductId   |   TotalQty
--------+---------------+---------------+------------
1       |   Paul        |   1           |   3
2       |   F           |   1           |   1
3       |   Francis     |   NULL        |   NULL

Answer 1

一种选择是使用WITH TIES 子句

Select Top 1 with ties 
       CustID
      ,CustName
      ,ProductId
      ,TotalQty
 From (
        Select  C.CustID
               ,C.CustName
               ,O.ProductId
               ,TotalQty = count(O.CustId) over (Partition By O.CustID)
               ,ProdCount = count(O.CustId) over (Partition By O.CustID,O.ProductID)
         From  #Cust  C
         Left  Join #Orders O on C.CustID=O.CustId
      ) A
 Order by Row_Number() over (Partition By CustID Order by ProdCount Desc) 

退货

CustID  CustName    ProductId   TotalQty
1       Paul        1           3
2       F           1           1
3       Francis     NULL        0