Pivoting table gives error : Must declare the scalar variable #start1 - sql

Question

Error :
Must declare the scalar variable "#start1".
Here is my query, I have two functions and am trying to pivot the data. The first function dbo.fxnExample accepts parameters is good but the second function dbo.fxnExample2 does not accept the parameters value, it pass 0 as the value.
ALTER proc [dbo].[SpTimesheetCrossTableFormat]
#start NVARCHAR(20),
#end NVARCHAR(20)
AS
BEGIN
DECLARE #DynamicPivotQuery AS NVARCHAR(MAX),
#PivotColumnNames AS NVARCHAR(MAX),
#PivotSelectColumnNames AS NVARCHAR(MAX)
DECLARE #start1 as nvarchar(20)=#start
DECLARE #start2 as nvarchar(20)=#end
--Get DISTINCT values of the PIVOT Column
SELECT #PivotColumnNames= convert(NVARCHAR(max),(ISNULL(#PivotColumnNames + ',','')))
+ CONVERT(NVARCHAR(max),(QUOTENAME(project_name)))
FROM (SELECT DISTINCT project_name FROM dbo.fxnExample(#start,#end)) AS project_name
--Get DISTINCT values of the PIVOT Column with isnull
SELECT #PivotSelectColumnNames
= ISNULL(#PivotSelectColumnNames + ',','')
+ 'ISNULL(' + QUOTENAME(project_name) + ', 0) AS '
+ QUOTENAME(project_name)
FROM (SELECT DISTINCT project_name FROM dbo.fxnExample(#start,#end)) AS project_name
--Prepare the PIVOT query using the dynamic
SET #DynamicPivotQuery =
N'SELECT d, user_name, ' + #PivotSelectColumnNames + '
FROM dbo.fxnExample2(#start1,#start2)
PIVOT(SUM(mins)
FOR project_name IN (' + #PivotColumnNames + ')) AS PVTTable'
--Execute the Dynamic Pivot Query
EXEC sp_executesql #DynamicPivotQuery
END
Here is the function :
CREATE FUNCTION [dbo].[fxnExample2] (#StartDate NVARCHAR(20),#EndDate NVARCHAR(20))
RETURNS TABLE
AS
RETURN
(
SELECT user_details.user_name,project_details.name as project_name,
--(ISNULL( DATEDIFF(mi,convert(datetime,punch_in,108), CONVERT(datetime,punch_out,108)),0)) as mins
[hours] as mins ,#StartDate as d
FROM timesheets
JOIN user_details
ON timesheets.user_id=user_details.id
JOIN project_details
ON timesheets.project_id=project_details.id
WHERE CONVERT(date, timesheets.tdate, 103) BETWEEN CONVERT(date, #StartDate, 103) and convert(date, #EndDate, 103)
--where CONVERT(date, tdate, 103) BETWEEN CONVERT(date, '15/08/2019', 103) AND CONVERT(date, '15/08/2019', 103)
)`
fnexample function
`CREATE FUNCTION [dbo].[fxnExample] (#StartDate nvarchar(20),#EndDate nvarchar(20))
RETURNS TABLE
AS
RETURN
(
SELECT user_details.user_name,project_details.name as project_name,
--(ISNULL( DATEDIFF(mi,CONVERT(datetime,punch_in,108), CONVERT(datetime,punch_out,108)),0)) as mins
[hours] as mins
FROM timesheets
JOIN user_details
ON timesheets.user_id=user_details.id
JOIN project_details
ON timesheets.project_id=project_details.id
WHERE CONVERT(date, tdate, 103) BETWEEN CONVERT(date, #StartDate, 103) AND CONVERT(date, #EndDate, 103)
--where CONVERT(date, tdate, 103) BETWEEN CONVERT(date, '05/08/2020', 103) AND CONVERT(date, '05/08/2019', 103)
)

Answer 1

Explanations about your error:
You are trying to execute a dynamic T-SQL statement using sp_executesql. If this statement contains parameters, you need to pass definitions of these parameters and their values to sp_executesql.
In your case, execute your statement in the following way:
EXEC sp_executesql
#DynamicPivotQuery,
N'#start1 as nvarchar(20), #start2 as nvarchar(20)',
#start1,
#start2
Notes:
It's good to check the result from sp_executesql call and optionally print this statement before the execution:
DECLARE #err int
PRINT #DynamicPivotQuery
EXEC #err = sp_executesql
#DynamicPivotQuery,
N'#start1 as nvarchar(20), #start2 as nvarchar(20)',
#start1,
#start2
IF #err = 0 PRINT 'OK' ELSE PRINT 'Error'