SQL Server：从联接表中的项目中获取行和总和答案

【问题标题】：SQL Server : get rows and sum from items in joined tableSQL Server：从联接表中的项目中获取行和总和
【发布时间】：2015-07-20 13:29:06
【问题描述】：

我想返回表 giftregistryitems 中的所有行以及一个额外的列，该列包含表 giftregistrypurchases 中列 amount 的总和，用于表 giftregistryitems 中的相应项目。

我尝试了什么，但是 purchasedamount 返回 NULL，我希望 purchasedamount 是该项目的 amount 的总和，基于 giftregistrypurchases.itemid = giftregistryitems.id：

SELECT 
   (SELECT 
        SUM(amount) 
    FROM
        giftregistrypurchases gps 
    WHERE  
        registryid = gi.registryid 
        AND gp.itemid = gps.itemid) as purchasedamount, * 
FROM 
    giftregistryitems gi
LEFT JOIN 
    giftregistrypurchases gp ON gp.registryid = gi.id
WHERE 
    gi.registryid = 2

我怎样才能达到我的需要？

这些是我的表定义和数据。

一点解释：

[giftregistry]是列表的一般描述，这里的新婚夫妇是唯一的所有者。他们可以添加要发送给客人的文本。

[giftregistryitems] 包含新婚夫妇请求的项目。这里的金额是他们想要的那个项目的总金额，例如6个咖啡杯。

[giftregistryemails] 包含来宾。

[giftregistrypurchases] 包含哪些客人购买了哪些商品的数量，例如客人编号3 购买了 5 个咖啡杯（总共 6 个）。

USE [tt]
GO
/****** Object: Table [dbo].[giftregistry] Script Date: 09-05-15 11:15:18 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[giftregistry](
[id] [int] IDENTITY(1,1) NOT NULL,
[listuuid] [nvarchar](50) NOT NULL CONSTRAINT [DF_giftregistry_listuuid] DEFAULT (newid()),
[userid] [nvarchar](50) NOT NULL,
[title] [nvarchar](50) NOT NULL,
[description] [nvarchar](500) NULL,
[invitetext] [nvarchar](1000) NULL,
[createdate] [datetime] NOT NULL CONSTRAINT [DF_giftregistry_createdate] DEFAULT (getdate()),
CONSTRAINT [PK_giftregistry] PRIMARY KEY CLUSTERED 
(
[id] 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].[giftregistryemails] Script Date: 09-05-15 11:15:18 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[giftregistryemails](
[id] [int] IDENTITY(1,1) NOT NULL,
[registryid] [int] NOT NULL,
[name] [nvarchar](50) NULL,
[email] [nvarchar](150) NOT NULL,
[pwd] [nvarchar](10) NULL,
[sentdate] [datetime] NULL CONSTRAINT [DF_giftregistryemails_sentdate] DEFAULT (((1)/(1))/(1900)),
[createdate] [datetime] NOT NULL CONSTRAINT [DF_giftregistryemails_createdate] DEFAULT (getdate()),
CONSTRAINT [PK_giftregistryemails] PRIMARY KEY CLUSTERED 
(
[id] 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].[giftregistryitems] Script Date: 09-05-15 11:15:18 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[giftregistryitems](
[id] [int] IDENTITY(1,1) NOT NULL,
[registryid] [int] NOT NULL,
[title] [nvarchar](500) NOT NULL,
[ogimg] [nvarchar](250) NULL,
[description] [nvarchar](500) NULL,
[URL] [nvarchar](500) NULL,
[trackingURL] [nvarchar](500) NULL,
[amount] [tinyint] NOT NULL,
[price] [int] NULL,
[createdate] [datetime] NOT NULL CONSTRAINT [DF_giftregistryitems_createdate] DEFAULT (getdate()),
CONSTRAINT [PK_giftregistryitems] PRIMARY KEY CLUSTERED 
(
[id] 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].[giftregistrypurchases] Script Date: 09-05-15 11:15:18 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[giftregistrypurchases](
[id] [int] IDENTITY(1,1) NOT NULL,
[registryid] [int] NOT NULL,
[itemid] [int] NOT NULL,
[emailid] [int] NOT NULL,
[amount] [tinyint] NOT NULL,
[createdate] [datetime] NOT NULL,
CONSTRAINT [PK_giftregistrypurchases] PRIMARY KEY CLUSTERED 
(
[id] 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].[giftregistry] ON 

GO
INSERT [dbo].[giftregistry] ([id], [listuuid], [userid], [title], [description], [invitetext], [createdate]) VALUES (2, N'83875b62-3cc1-4516-b932-6e60a116cbff', N'32DD30EB-1691-457B-9FF5-FC41D687E579', N'My list', N'We''re getting married', N'Hey you guys coming too?', CAST(N'2015-04-29 21:21:53.813' AS DateTime))
GO
SET IDENTITY_INSERT [dbo].[giftregistry] OFF
GO
SET IDENTITY_INSERT [dbo].[giftregistryemails] ON 

GO
INSERT [dbo].[giftregistryemails] ([id], [registryid], [name], [email], [pwd], [sentdate], [createdate]) VALUES (2, 2, N'Peter', N'peter@hotmail.com', N'1234', CAST(N'1900-01-01 00:00:00.000' AS DateTime), CAST(N'2015-05-02 22:01:53.783' AS DateTime))
GO
INSERT [dbo].[giftregistryemails] ([id], [registryid], [name], [email], [pwd], [sentdate], [createdate]) VALUES (3, 2, N'Eric', N'eric@outlook.com', N'1234', CAST(N'1900-01-01 00:00:00.000' AS DateTime), CAST(N'2015-05-02 22:01:53.783' AS DateTime))
GO
SET IDENTITY_INSERT [dbo].[giftregistryemails] OFF
GO
SET IDENTITY_INSERT [dbo].[giftregistryitems] ON 

GO
INSERT [dbo].[giftregistryitems] ([id], [registryid], [title], [ogimg], [description], [URL], [trackingURL], [amount], [price], [createdate]) VALUES (9, 2, N'1111', N'http://i.ebayimg.com/images/i/281656969697-0-1/s-l1000.jpg', N'Surface Pro 3', N'http://www.ebay.com/itm/Microsoft-Surface-Pro-3-12-Tablet-256GB-SSD-Intel-Core-i7-Haswell-8GB-RAM-/281656969697', NULL, 1, 114998, CAST(N'2015-05-05 20:06:57.143' AS DateTime))
GO
INSERT [dbo].[giftregistryitems] ([id], [registryid], [title], [ogimg], [description], [URL], [trackingURL], [amount], [price], [createdate]) VALUES (10, 2, N'Coffee cups', N'http://www.trouwen-feestartikelen.nl/images/rozenblaadjes-burgundy.jpg', N'Great cups', N'https://www.coffee.com/cups', NULL, 6, 25, CAST(N'2015-05-05 20:57:05.900' AS DateTime))
GO
SET IDENTITY_INSERT [dbo].[giftregistryitems] OFF
GO
SET IDENTITY_INSERT [dbo].[giftregistrypurchases] ON 
GO
INSERT [dbo].[giftregistrypurchases] ([id], [registryid], [itemid], [emailid], [amount], [createdate]) VALUES (3, 2, 9, 2, 5, CAST(N'2015-05-09 11:18:12.000' AS DateTime))
GO
SET IDENTITY_INSERT [dbo].[giftregistrypurchases] OFF
GO

ALTER TABLE [dbo].[giftregistrypurchases] ADD CONSTRAINT [DF_giftregistrypurchases_createdate] DEFAULT (getdate()) FOR [createdate]
GO
ALTER TABLE [dbo].[giftregistryemails] WITH CHECK ADD CONSTRAINT [FK_giftregistryemails_giftregistry] FOREIGN KEY([registryid])
REFERENCES [dbo].[giftregistry] ([id])
ON DELETE CASCADE
GO
ALTER TABLE [dbo].[giftregistryemails] CHECK CONSTRAINT [FK_giftregistryemails_giftregistry]
GO
ALTER TABLE [dbo].[giftregistryitems] WITH CHECK ADD CONSTRAINT [FK_giftregistryitems_giftregistry] FOREIGN KEY([registryid])
REFERENCES [dbo].[giftregistry] ([id])
ON DELETE CASCADE
GO
ALTER TABLE [dbo].[giftregistryitems] CHECK CONSTRAINT [FK_giftregistryitems_giftregistry]
GO
ALTER TABLE [dbo].[giftregistrypurchases] WITH CHECK ADD CONSTRAINT [FK_giftregistrypurchases_giftregistryitems] FOREIGN KEY([itemid])
REFERENCES [dbo].[giftregistryitems] ([id])
ON DELETE CASCADE
GO
ALTER TABLE [dbo].[giftregistrypurchases] CHECK CONSTRAINT [FK_giftregistrypurchases_giftregistryitems]
GO
EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'the unique code for this list' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N'giftregistry', @level2type=N'COLUMN',@level2name=N'listuuid'
GO
EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'the generated password for this list and this user' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N'giftregistryemails', @level2type=N'COLUMN',@level2name=N'pwd'
GO
EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'The user pasted URL is converted to a tracking URL where possible' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N'giftregistryitems', @level2type=N'COLUMN',@level2name=N'trackingURL'
GO

期望的结果：

purchasedamount id  registryid  title   ogimg   description URL amount  price   createdate
5   4   2   Coffee cups http://www.trouwen-feestartikelen.nl/images/rozenblaadjes-burgundy.jpg  Great cups  https://www.coffee.com/cups 6   25  57:05.9
0   5   2   Surface Pro 3   http://i.ebayimg.com/images/i/281656969697-0-1/s-l1000.jpg  Surface Pro 3   http://www.ebay.com/itm/Microsoft-Surface-Pro-3-12-Tablet-256GB-SSD-Intel-Core-i7-Haswell-8GB-RAM-/281656969697 1   114998  06:57.1

【问题讨论】：

标签： sql-server tsql sql-server-2012

【解决方案1】：

2 种好方法：

1) 按（很多东西）分组

SELECT    
    SUM(gi.amount) as amount,
    gp.* 
FROM 
    giftregistryitems gi
LEFT JOIN 
    giftregistrypurchases gp ON gp.registryid = gi.id
WHERE 
    gi.registryid = 2
group by
    gp.Field1,
    gp.Field2 --All the gp fields :)

2) 子查询（如果我是你，我会这样做）

select
    *,
    (select sum(gi.amount) from giftregistryitems gi where gp.registryid = gi.id)
from
    giftregistrypurchases gp

干杯！

【讨论】：

嗨，您的代码对表 giftregistryitems 中的 amount 求和。这不是我想要的：我想为giftregistryitems 中的每个项目对表giftregistrypurchases 中的amount 列求和。我该怎么做？
嗨，弗洛，很抱歉，但我不确定我是否按照您的要求进行操作。如果你给我另一个带数字的例子，我很乐意提供另一个答案:) 再次阅读你的例子，我得出了这个结论，如果这不是你想要的，我很抱歉，但我不确定我是否完全理解你期待什么:)
select *, (select sum(gp.amount) from giftregistrypurchases gp where gp.registryid = gi.registryid and gp.itemid = gi.id) from giftregistryitems gi

【解决方案2】：

SELECT gi.ID, SUM(gps.amount) as purchasedamount
FROM 
    giftregistryitems gi
LEFT JOIN 
    giftregistrypurchases gp ON gp.registryid = gi.id
WHERE 
    gi.registryid = 2
group by gi.id

如果 registryid 在两个表中的含义不同，这是一个不好的命名约定。

【讨论】：