Adventure Works 2014 SQL查询

Question

我正在使用Adventure Works 2014数据库编写SQL查询。

我想向所有客户展示每个客户的订单数量。

我试图自己编写每个select语句（见下文），但我希望能够将两个查询合并为一个。

select  s.CustomerID ,p.FirstName +' '+p.LastName as Name 
from Sales.Customer s,Person.Person p 
where s.CustomerID=p.BusinessEntityID
order by s.CustomerID


select CustomerID ,count(SalesOrderID) as OrdersCount
from Sales.SalesOrderHeader
group by CustomerID

Answer 1

 SELECT s.CustomerID ,
        p.FirstName +' '+p.LastName as Name,
        count(SalesOrderID)
 FROM Sales.Customer s
 JOIN Person.Person p 
   ON s.CustomerID=p.BusinessEntityID
 LEFT JOIN Sales.SalesOrderHeader so
   ON s.Customer_ID = so.Customer_ID  
 GROUP BY s.CustomerID ,
        p.FirstName +' '+p.LastName as Name 
 order by s.CustomerID

Answer 2

我添加了CONCAT，可能对您来说是新东西。无论如何，OVER（PARTITION BY column_name ）子句被用作GROUP BY的替代，因为您打印的列比GROUP BY子句所允许的多。

Answer 3

表Sales.Customer 参考：Person.Person（PersonID-> BusinessEntityID）

SELECT s.CustomerID 
        ,p.FirstName +' '+p.LastName as Name
        ,COUNT(so.SalesOrderDetailID)
 FROM Sales.Customer s
 JOIN Person.Person p 
   ON s.PersonID=p.BusinessEntityID
 LEFT JOIN Sales.SalesOrderHeader h 
   ON h.CustomerID = s.CustomerID
 LEFT JOIN Sales.SalesOrderDetail so
   ON so.SalesOrderID = h.SalesOrderID
 GROUP BY s.CustomerID ,
        p.FirstName +' '+p.LastName
 order by s.CustomerID