SQL Inner customers with orders

Question

如果我有两个表(一个是customers，包含他们的信息，包括地址、姓名、电子邮件等)，另一个是orders (包含订单号、发货日期、订购该商品的客户名称)，我如何显示少于3个订单的客户的电子邮件？

我知道我必须使用内部连接和一些别名，但我不确定如何继续。

谢谢!

到目前为止，我所拥有的：

SELECT customer.email 
FROM customer as cust 
INNER JOIN (select customer_id, sum(line_qty) AS total 
            from orders as o ON cust.customer_id = o.customer_id 
            where total = (SELECT total < 3 
                           FROM (select customer_id, sum(line_qty) AS total 
                                 from orders as o ON cust.customer_id = o.customer_id
                                ) as sub);

Answer 1

我已经用SQL创建了完整的示例。只需运行该查询即可创建数据库、表和存储过程"Get Customer Orders“。

在两个"Customers“表和" Orders”表中有示例数据，关系是"1个客户对多个订单“，因此表Orders中的Customer有一个外键，用于识别哪个客户完成了订单。所以。

首先创建数据库，运行以下查询。

Create DataBase [Customer_OrdersDB]

刷新服务器资源管理器，您会发现已经创建了一个同名的数据库。然后运行查询以创建存储过程和表。

    USE [Customer_OrdersDB]
GO
CREATE PROCEDURE [dbo].[GetCustomer_Mail] 
AS
BEGIN
select Email as Customer_Mail 
from Customers as cust inner join Orders as ord
on cust.CustomerId = ord.OrderCustomerId
group by(Email)
having COUNT(ord.OrderCustomerId) < 3
END

GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Customers](
    [CustomerId] [int] IDENTITY(1,1) NOT NULL,
    [CustomerName] [nvarchar](50) NULL,
    [Address] [nvarchar](50) NULL,
    [Email] [nvarchar](50) NULL,
 CONSTRAINT [PK_Customers] PRIMARY KEY CLUSTERED 
(
    [CustomerId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
/****** Object:  Table [dbo].[Orders]    Script Date: 12/6/2014 5:19:11 AM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Orders](
    [OrderId] [int] IDENTITY(1,1) NOT NULL,
    [OrderDate] [datetime] NULL,
    [OrderNumber] [nvarchar](50) NULL,
    [OrderCustomerId] [int] NULL,
 CONSTRAINT [PK_Orders] PRIMARY KEY CLUSTERED 
(
    [OrderId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
SET IDENTITY_INSERT [dbo].[Customers] ON 

INSERT [dbo].[Customers] ([CustomerId], [CustomerName], [Address], [Email]) VALUES (1, N'Ahmed', N'Cairo', N'Ahmed@Yahoo.Com')
INSERT [dbo].[Customers] ([CustomerId], [CustomerName], [Address], [Email]) VALUES (2, N'Ali', N'Paris', N'Ali@yahoo.com')
INSERT [dbo].[Customers] ([CustomerId], [CustomerName], [Address], [Email]) VALUES (3, N'Samir', N'UK', N'Samir@msn.com')
SET IDENTITY_INSERT [dbo].[Customers] OFF
SET IDENTITY_INSERT [dbo].[Orders] ON 

INSERT [dbo].[Orders] ([OrderId], [OrderDate], [OrderNumber], [OrderCustomerId]) VALUES (1, CAST(0x0000A2A600000000 AS DateTime), N'1234', 1)
INSERT [dbo].[Orders] ([OrderId], [OrderDate], [OrderNumber], [OrderCustomerId]) VALUES (2, CAST(0x0000A2C700000000 AS DateTime), N'555', 1)
INSERT [dbo].[Orders] ([OrderId], [OrderDate], [OrderNumber], [OrderCustomerId]) VALUES (3, CAST(0x00009CF100000000 AS DateTime), N'56d66', 1)
INSERT [dbo].[Orders] ([OrderId], [OrderDate], [OrderNumber], [OrderCustomerId]) VALUES (4, CAST(0x00009E9B00000000 AS DateTime), N'555we', 2)
INSERT [dbo].[Orders] ([OrderId], [OrderDate], [OrderNumber], [OrderCustomerId]) VALUES (5, CAST(0x0000A2A600000000 AS DateTime), N'1234', 1)
INSERT [dbo].[Orders] ([OrderId], [OrderDate], [OrderNumber], [OrderCustomerId]) VALUES (6, CAST(0x0000A2C700000000 AS DateTime), N'555', 1)
SET IDENTITY_INSERT [dbo].[Orders] OFF
ALTER TABLE [dbo].[Orders]  WITH CHECK ADD  CONSTRAINT [FK_Orders_Customers] FOREIGN KEY([OrderCustomerId])
REFERENCES [dbo].[Customers] ([CustomerId])
GO
ALTER TABLE [dbo].[Orders] CHECK CONSTRAINT [FK_Orders_Customers]
GO

然后，为了访问您的存储过程，如果他/她的订单少于3个，您希望获得客户的电子邮件。

在

1. 中，转到服务器/对象资源管理器。
2. 选择名为

的数据库单击您的存储过程"GetCustomer_Mail“，然后选择Execute。

Answer 2

试试这个：

SELECT c.email 
FROM customer AS c 
LEFT OUTER JOIN orders AS o ON c.customer_id = o.customer_id 
GROUP BY c.email 
HAVING SUM(o.line_qty) < 3