在更改数据类型时旋转（动态）

Question

假设我有 3 个表：users、customattributes 和 customattributevalues。最终用户可以通过选择属性的名称和类型来添加自定义属性，并为任何用户编辑值。

这是我的用户：

id	firstname	lastname	active	datecreated	username	email
3	Ellen	Ripley	1	3/25/2235	78439	Rip8439@Weyland-Yutani.com
5	Johnny	Rico	1	4/16/2675	Roughneck31	RicoJ31@Roughnecks.com

自定义属性（可以随时添加）

id	fullname	uniquename	type
1	Hire Date	hiredate	date
2	Employee ID	eeid	int
3	Supervisor	supervisor	nvarchar(50)
4	Assigned Ship	assignedship	nvarchar(50)
5	Job Title	jobtitle	nvarchar(50)

我目前拥有的类型为 sysname 数据类型。

自定义属性值（可以随时编辑）

id	attributeid	userid	value
1	1	3	2335-03-25
2	2	3	78439
3	3	3	Burke, Carter
4	4	3	Sulaco
5	5	3	Consultant
6	1	5	2675-04-16
7	2	5	78440
8	3	5	LT Rasczak
9	4	5	Rodger Young
10	5	5	Private

我目前拥有sql_variant 数据类型的值

所以这是我的问题：如何在不知道有多少自定义属性的情况下创建一个显示所有员工及其属性的报告，每个员工 1 行 -- 并且 -- 至关重要的是，我想明确将每一列转换为正确的数据类型

期望的输出：

firstname	lastname	datecreated	username	email	Hire Date	Employee ID	Supervisor	Assigned Ship	Job Title
Ellen	Ripley	2235-03-25	78439	Rip8439@Weyland-Yutani.com	2335-03-25	78439	Burke, Carter	Sulaco	Consultant
Johnnie	Rico	2675-04-16	Roughneck31	RicoJ31@Roughnecks.com	2675-04-16	78440	LT Rasczak	Rodger Young	Private

我已经学会了使用dynamic queries 来做动态列标题，但这是我逃避的类型转换。

我正在适应this solution for custom fields，但此解决方案的限制是您必须知道每个自定义字段才能进行类型转换。

这是我尝试过的。我得到了正确的输出，除了类型转换。

查询：

DECLARE @columns NVARCHAR(MAX) = '';
DECLARE @sqlcmd NVARCHAR(MAX) = '';

SELECT @columns += QUOTENAME(fullname) + ','
FROM customattributesx ca

ORDER BY ca.id;

SET @columns = LEFT(@columns, LEN(@columns) - 1);

--PRINT @columns;

SET @sqlcmd = '
SELECT * FROM (
    SELECT userid
        ,firstname
        ,lastname
        ,datecreated
        ,username
        ,email
        ,fullname
        ,value
    FROM (
        SELECT u.id as userid
              ,u.firstname
              ,u.lastname
              ,u.datecreated
              ,u.username
              ,u.email
              ,ca.id
              ,ca.fullname as fullname
              ,ca.uniquename
              ,ca.type
              ,cav.value as value
        FROM dbo.users u
        CROSS JOIN customattributesx ca
        INNER JOIN customattributevaluesx cav
            ON cav.attributeid = ca.id AND cav.userid = u.id

        --ORDER BY u.id asc, ca.id asc
    ) t1
) t2
PIVOT (
    MIN(value)
    FOR fullname IN ('+@columns+')
) as pivottable
';
--print @sqlcmd
EXECUTE (@sqlcmd)

创建表：

USE [CTMS]
GO

/****** Object:  Table [dbo].[users]    Script Date: 11/24/2021 9:29:16 AM ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[users](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [firstname] [nvarchar](max) NULL,
    [lastname] [nvarchar](max) NULL,
    [active] [bit] NOT NULL,
    [datecreated] [datetime2](7) NOT NULL,
    [username] [nvarchar](256) NULL,
    [email] [nvarchar](256) NULL,
    [emailconfirmed] [bit] NOT NULL,
    [passwordhash] [nvarchar](max) NULL,
    [twofactorenabled] [bit] NOT NULL,
    [lockoutend] [datetimeoffset](7) NULL,
    [eockoutenabled] [bit] NOT NULL,
    [accessfailedcount] [int] NOT NULL,
    [qrcode] [nvarchar](50) NULL,
 CONSTRAINT [PK_id] PRIMARY KEY CLUSTERED 
(
    [id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY],
 CONSTRAINT [uk_email] UNIQUE NONCLUSTERED 
(
    [email] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY],
 CONSTRAINT [uk_qrcode] UNIQUE NONCLUSTERED 
(
    [qrcode] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY],
 CONSTRAINT [uk_username] UNIQUE NONCLUSTERED 
(
    [username] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO

ALTER TABLE [dbo].[users] ADD  DEFAULT (getutcdate()) FOR [datecreated]
GO


USE [CTMS]
GO

/****** Object:  Table [dbo].[customattributesx]    Script Date: 11/24/2021 9:31:09 AM ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[customattributesx](
    [id] [smallint] IDENTITY(1,1) NOT NULL,
    [fullname] [nvarchar](50) NOT NULL,
    [uniquename] [nvarchar](50) NOT NULL,
    [type] [sysname] NOT NULL,
 CONSTRAINT [PK_customattributesx] PRIMARY KEY CLUSTERED 
(
    [id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY],
 CONSTRAINT [uk1_customattributesx] UNIQUE NONCLUSTERED 
(
    [uniquename] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO

USE [CTMS]
GO

/****** Object:  Table [dbo].[customattributevaluesx]    Script Date: 11/24/2021 9:31:27 AM ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[customattributevaluesx](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [attributeid] [smallint] NOT NULL,
    [userid] [int] NOT NULL,
    [value] [sql_variant] NOT NULL,
 CONSTRAINT [PK_customattributevaluesx] PRIMARY KEY CLUSTERED 
(
    [id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY],
 CONSTRAINT [uk1_customattributevaluesx] UNIQUE NONCLUSTERED 
(
    [attributeid] ASC,
    [userid] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[customattributevaluesx]  WITH CHECK ADD  CONSTRAINT [fk1_customattributesvaluesx] FOREIGN KEY([attributeid])
REFERENCES [dbo].[customattributesx] ([id])
GO

ALTER TABLE [dbo].[customattributevaluesx] CHECK CONSTRAINT [fk1_customattributesvaluesx]
GO

ALTER TABLE [dbo].[customattributevaluesx]  WITH CHECK ADD  CONSTRAINT [fk2_customattributesvaluesx] FOREIGN KEY([userid])
REFERENCES [dbo].[users] ([id])
GO

ALTER TABLE [dbo].[customattributevaluesx] CHECK CONSTRAINT [fk2_customattributesvaluesx]
GO

Answer 1

如果您必须转换数据类型（可能真的是表示层的事情），那么动态条件聚合应该可以解决问题。

示例

Declare @SQL nvarchar(max) ='
Select U.*' +
(
Select concat(',',quotename(fullname),'=max(case when attributeid=',id,' then try_convert(',type,',value) end)')
 From customattributes
 For XML Path ('')
)+'
 From  users U
 Join  customattributesvalues V on U.ID=V.userid
 Group By U.ID
         ,U.FirstName
         ,U.LastName
         ,U.active
         ,U.datecreated
         ,U.username
         ,U.email
'
--print @SQL
Exec(@SQL)

结果

生成的 SQL 如下所示

Select U.*
      ,[Hire Date]=max(case when attributeid=1 then try_convert(date,value) end)
      ,[Employee ID]=max(case when attributeid=2 then try_convert(int,value) end)
      ,[Supervisor]=max(case when attributeid=3 then try_convert(nvarchar(50),value) end)
      ,[Assigned Ship]=max(case when attributeid=4 then try_convert(nvarchar(50),value) end)
      ,[Job Title]=max(case when attributeid=5 then try_convert(nvarchar(50),value) end)
 From  #users U
 Join  #customattributesvalues V on U.ID=V.userid
 Group By U.ID
         ,U.FirstName
         ,U.LastName
         ,U.active
         ,U.datecreated
         ,U.username
         ,U.email

Answer 2

SQL_VARIANT 可以转换为目标数据类型。

修改生成列列表的动态查询部分，生成两个列表。一个列表用于PIVOT 部分，另一个用于SELECT 部分，您可以在其中转换数据类型。

示例基于article you refer to in your question:

DECLARE @PivotList NVARCHAR( MAX )
DECLARE @SelectList NVARCHAR( MAX )
SELECT @SelectList = NULL, @PivotList = NULL
        -- Column list with CAST e.g. CAST( eeid AS INT ) AS eeid
        -- Data types come from your customattributes table
SELECT @SelectList = COALESCE( @SelectList + ',','') + 'CAST( ' + uniquename + ' AS [type] ) AS ' + uniquename,
        -- Just a column list that goes into PIVOT operator
        @PivotList = COALESCE( @PivotList + ',','') + uniquename
-- Your tables for attribute values and attribute type definitions
FROM customattributes AS ca

DECLARE @SQLQuery NVARCHAR(MAX)
SET @SQLQuery =

'SELECT StudID , '+@SelectList+'
FROM
( SELECT SM.StudID, S.SubjectName, SM.Score 
FROM StudentMarks SM 
INNER JOIN Subjects S
ON Sm.SubjectID = S.SubjectID
) AS tbl
PIVOT 
( Sum(Score)
FOR SubjectName IN ('+@PivotList+') ) as pvt'

EXEC(@SQLQuery)