Question

我有三个表TableA，TableB，TableC和Table A都有数百万条记录。

表A具有AccountId，表B具有accountId，客户及其证书，而表C具有证书。

情况是，表B中的AccountId具有多个具有多个证书的客户端。

当我尝试通过连接表B和C从表A中获取数据时，它会获取重复的记录，因为表B中的AccountId具有多个带有多个证书的客户端。

您可以使用此脚本填充表和数据以测试情况

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[TableA]
(
    [AccountId] [int] NOT NULL,
    [Name] [nvarchar](50) NULL,
    [Mobile] [nchar](10) NULL,
 CONSTRAINT [PK_Accounts] PRIMARY KEY CLUSTERED 
(
    [AccountId] 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 ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[TableB]
(
    [Id] [int] NOT NULL,
    [ClientId] [int] NOT NULL,
    [CertificateId] [int] NOT NULL,
    [AccountId] [int] NOT NULL,
 CONSTRAINT [PK_TableB] PRIMARY KEY CLUSTERED 
(
    [Id] ASC,
    [ClientId] ASC,
    [CertificateId] 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 ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[TableC]
(
    [CertificateId] [int] NOT NULL,
    [Status] [bit] NOT NULL,
    [Description] [nvarchar](50) NULL,
 CONSTRAINT [PK_TableC] PRIMARY KEY CLUSTERED 
(
    [CertificateId] 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

INSERT [dbo].[TableA] ([AccountId], [Name], [Mobile]) VALUES (1, N'John', N'98        ')
INSERT [dbo].[TableA] ([AccountId], [Name], [Mobile]) VALUES (2, N'Henry', N'9808      ')
INSERT [dbo].[TableA] ([AccountId], [Name], [Mobile]) VALUES (3, N'Paine', N'9045      ')
INSERT [dbo].[TableA] ([AccountId], [Name], [Mobile]) VALUES (4, N'Andrew', N'887       ')
INSERT [dbo].[TableA] ([AccountId], [Name], [Mobile]) VALUES (5, N'Stocks', N'78        ')
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (1, 5, 34, 1)
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (2, 8, 34, 1)
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (3, 7, 36, 2)
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (4, 9, 37, 3)
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (5, 10, 37, 4)
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (6, 4, 37, 4)
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (7, 61, 37, 4)
INSERT [dbo].[TableB] ([Id], [ClientId], [CertificateId], [AccountId]) VALUES (8, 45, 35, 5)
INSERT [dbo].[TableC] ([CertificateId], [Status], [Description]) VALUES (34, 1, N'Certificate 1')
INSERT [dbo].[TableC] ([CertificateId], [Status], [Description]) VALUES (35, 1, N'Certificate 2')
INSERT [dbo].[TableC] ([CertificateId], [Status], [Description]) VALUES (36, 1, N'Certificate 3')
INSERT [dbo].[TableC] ([CertificateId], [Status], [Description]) VALUES (37, 0, N'Certificate 4')
ALTER TABLE [dbo].[TableB]  WITH CHECK ADD  CONSTRAINT [FK_TableB_TableA] FOREIGN KEY([AccountId])
REFERENCES [dbo].[TableA] ([AccountId])
GO
ALTER TABLE [dbo].[TableB] CHECK CONSTRAINT [FK_TableB_TableA]
GO
ALTER TABLE [dbo].[TableB]  WITH CHECK ADD  CONSTRAINT [FK_TableB_TableC] FOREIGN KEY([CertificateId])
REFERENCES [dbo].[TableC] ([CertificateId])
GO
ALTER TABLE [dbo].[TableB] CHECK CONSTRAINT [FK_TableB_TableC]
GO

我的查询

DECLARE @From int=1
DECLARE @To int=5
; WITH CTE_Data_WITH_PAGING  AS 
  (SELECT ROW_NUMBER() OVER( ORDER BY A.AccountId) AS [ROW_NUMBERS], 
        A.AccountId, A.Name, A.Mobile FROM TableA A
        LEFT JOIN  TableB B  
        ON B.AccountId = A.AccountId
        INNER JOIN TableC C
        ON C.CertificateId=B.CertificateId 
        AND C.CertificateId<>01

        )
        SELECT  * FROM CTE_Data_WITH_PAGING WHERE ROW_NUMBERS BETWEEN @From AND @To;

我尝试以这种方式使用与众不同的方法，但分页问题。

SELECT DISTINCT(AccountId), Name, Mobile 
FROM CTE_Data_WITH_PAGING 
WHERE ROW_NUMBERS BETWEEN @From AND @To;

分页问题：尝试@ from = 1 @ to = 4并查看输出，它应该获得AccountId：1，2，3,4

Answer 1

一种快速的解决方法是改用density_rank并结合使用distinct。这样可以确保每个帐户都被计数。还按照注释中的建议使用内部联接：

DECLARE @From int=1
DECLARE @To int=5
; WITH CTE_Data_WITH_PAGING  AS 
  (SELECT distinct dense_rank() OVER( ORDER BY A.AccountId) AS [ROW_NUMBERS], 
    A.AccountId, A.Name, A.Mobile FROM TableA A
    inner JOIN  TableB B  
    ON B.AccountId = A.AccountId
    INNER JOIN TableC C
    ON C.CertificateId=B.CertificateId 
    AND C.CertificateId<>01

    )
    SELECT  * FROM CTE_Data_WITH_PAGING WHERE ROW_NUMBERS BETWEEN @From AND @To;

我倾向于使用分组方式，而不是使用分组方式-尤其是与分析功能结合使用，因此使用row_number可能是：

DECLARE @From int=1
DECLARE @To int=5
; WITH CTE_Data_WITH_PAGING  AS 
  (SELECT  row_number() OVER( ORDER BY A.AccountId) AS [ROW_NUMBERS], 
    A.AccountId, A.Name, A.Mobile FROM TableA A
    inner JOIN  TableB B  
    ON B.AccountId = A.AccountId
    INNER JOIN TableC C
    ON C.CertificateId=B.CertificateId 
    AND C.CertificateId<>01
    group by  A.AccountId, A.Name, A.Mobile
    )
    SELECT  * FROM CTE_Data_WITH_PAGING WHERE ROW_NUMBERS BETWEEN @From AND @To;

我在此处分组以获取唯一值。

最后，如果您只是在其中进行分页，并且不需要行号，则只需使用OFFSET和FETCH，如下所示：

DECLARE @From int = 1 宣告@To int = 5

 SELECT  
  A.AccountId, A.Name, A.Mobile FROM TableA A
  inner JOIN  TableB B  
  ON B.AccountId = A.AccountId
  INNER JOIN TableC C
  ON C.CertificateId=B.CertificateId 
  AND C.CertificateId<>01
 group by  A.AccountId, A.Name, A.Mobile
 order by  A.AccountId
 OFFSET (@FROM-1) ROWS FETCH NEXT (@TO-(@FROM-1)) ROWS ONLY;

通过分页使用CTE从3个表中获取记录

1 个答案: