SQL服務器查詢：如何選擇多個訂單的客戶

Question

我是一個SQL服務器新手，並試圖選擇所有擁有多個1 orderid的客戶。該表如下所示：

CREATE TABLE [dbo].[orders](
    [customerid] [int] NULL, 
    [orderid] [int] NULL 
) ON [PRIMARY] 
GO 
INSERT [dbo].[orders] ([customerid], [orderid]) VALUES (1, 2) 
INSERT [dbo].[orders] ([customerid], [orderid]) VALUES (1, 3) 
INSERT [dbo].[orders] ([customerid], [orderid]) VALUES (2, 4) 
INSERT [dbo].[orders] ([customerid], [orderid]) VALUES (2, 5) 
INSERT [dbo].[orders] ([customerid], [orderid]) VALUES (3, 1) 

Answer 1

select customerid 
,  count(*) as order_count 
from orders 
group by 
     customerid 
having count(*) > 1