删除左连接SQL Server中的重复项

Question

我在最终结果中有重复。我尝试使用Distinct以及group by子句。

Select distinct   
    Orders.OrderNumber, Tracking.TrackingID, 
    Orders.BalanceDue, Orders.Approved, Orders.Name, Orders.ShipCity ,  
    Orders.OrderDate, Orders.country, Orders.Shipping, Orders.CartId
from  
    orders
left join 
    Tracking on Orders.OrderNumber = Tracking.ordernum 
group by 
    Orders.OrderNumber, Orders.BalanceDue, Tracking.TrackingID, 
    Orders.Approved, Orders.Name, Orders.ShipCity, 
    Orders.OrderDate, Orders.country, Orders.Shipping, Orders.CartId

Orders表中有8166行，我想在最终结果中只有那么多列。

！[在此输入图片说明] [3]

Answer 1

获取一个跟踪ID的一种方法是使用聚合函数和从trackingid子句中删除group by：

Select o.OrderNumber, max(t.TrackingID) as TrackingId,
       o.BalanceDue, o.Approved, o.Name, o.ShipCity,  
       o.OrderDate, o.country, o.Shipping, o.CartId
from orders l left join 
     Tracking t
     on o.OrderNumber = t.ordernum 
group by o.OrderNumber, o.BalanceDue, o.Approved, o.Name, o.ShipCity, 
         o.OrderDate, o.country, o.Shipping, o.CartId;