Pivot while changing data types (dynamically) - sql

Question

Let's say I have 3 tables: users, customattributes, and customattributevalues. End user can add custom attributes by selecting a name and type for the attribute, and the edit the values for any user.
Here are my users:
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
customattributes (can be added to anytime)
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)
type I currently have as sysname datatype.
customattributevalues (can be edited anytime)
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
value I currently have as sql_variant datatype
So here is my question: how can I create a report that shows all employees and their attributes, 1 line per employee, without knowing how many custom attributes there are --and-- crucially, I want to explicitly convert each column to the correct data type
Desired output:
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
I've already learned to do the dynamic column headers using dynamic queries, but it is the type conversion that is escaping me.
I'm adapting this solution for custom fields, but the limitation to this solution is you have to know each custom field to make the type conversion.
Here is what I've tried. I got the correct output, except for the type conversions.
Query:
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)
Create Tables:
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

If you must convert the datatype (could really be a presentation layer thing), then a dynamic conditional aggregation should do the trick.
Example
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)
Results
The Generated SQL Looks Like This
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 can be cast to a destination data type.
Modify part of the dynamic query where you generate column list, to generate two lists. One list is for PIVOT part and the other for SELECT part where you cast you data types.
Example is based on the 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)