查询上市公司名称及首单日期答案

【问题标题】：Query listing company name and first order date查询上市公司名称及首单日期
【发布时间】：2013-12-27 05:54:29
【问题描述】：

正如标题所说，我正在尝试编写一个查询来显示客户 ID、公司名称和他们的第一个订单日期（列出的最早日期）。我试过Top 1，但没有用。使用 SQL Server 2012。

Select c.CustomerID, CompanyName, top 1 o.OrderDate as 'first order date'
from Customers c join Orders o on
c.CustomerID = o.CustomerID 
order by c.CustomerID

任何建议或帮助将不胜感激！

【问题讨论】：

标签： sql sql-server-2012 filtering

【解决方案1】：

select c.CustomerID, CompanyName, MIN(o.OrderDate) as 'first order date'
from
    Customers c
    join Orders o on c.CustomerID = o.CustomerID
group by c.CustomerID, CompanyName 
order by c.CustomerID

【讨论】：

【解决方案2】：

此解决方案更加灵活，因为它允许您从Customers 表中添加任何列，而无需将它们添加到GROUP BY：

;WITH x AS 
(
  SELECT CustomerID, OrderDate = MIN(OrderDate)
  FROM dbo.Orders GROUP BY CustomerID
)
SELECT c.CustomerID, c.CompanyName, x.OrderDate
  FROM dbo.Customers AS c
  INNER JOIN x ON c.CustomerID = x.CustomerID
  ORDER BY c.CustomerID;

如果您还想要第一个订单的其他列，例如订单总额，您可以这样做，使用 GROUP BY 时无法添加，因为例如最便宜或最昂贵的订单不会必然对应一阶：

;WITH x AS 
(
  SELECT CustomerID, OrderDate, TotalAmount, /* ...other columns... */
    rn = ROW_NUMBER() OVER (PARTITION BY CustomerID ORDER BY OrderDate)
  FROM dbo.Orders GROUP BY CustomerID
)
SELECT c.CustomerID, c.CompanyName, x.OrderDate, x.TotalAmount /* ...others... */
  FROM dbo.Customers AS c
  INNER JOIN x ON c.CustomerID = x.CustomerID
  WHERE x.rn = 1
  ORDER BY c.CustomerID;

【讨论】：