Unpivot using Dynamic query - sql-server

Question

I am writing a query to unpivot any table as required, based on it's first column and a selected row. And I am facing an issue in the dynamic query. The actual table has 77 columns with different data type that I tried to convert it to varchar and the values will always be of a particular row of a table.
example:
CREATE TABLE EXAMPLE (ROWDATA INT, CHARDATA VARCHAR(MAX), BIGINTCOLUMN BIGINT)
INSERT INTO EXAMPLE (ROWDATA INT, CHARDATA VARCHAR(MAX), BIGINTCOLUMN BIGINT)
VALUES (1, AB, 15698), (2, BD, 23467), (3, ABC, 42378)
Now I want to do unpivot operation without putting columns so that I can use it for multiple purpose and there should only be 2 columns one is ColumnName that contains value
"CHARDATA,BIGINTCOLUMN" other ColumnValue that contains value like "BD,23467" or "ABC,42378" '
CODE:
create table #ColumnName (Countno int identity(1,1), Column_Name varchar(max))
insert into #ColumnName (Column_Name) select COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'EXAMPLE'
Create table #Converttype (Countno int identity(1,1), Converttype varchar(max))
insert into #Converttype (Converttype) select case when DATA_TYPE <> 'varchar' then 'Cast(' + COLUMN_NAME + ' as varchar) as '+ COLUMN_NAME else COLUMN_NAME end from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'EXAMPLE'
declare #CreateTable varchar(max) =(select Column_Name from #ColumnName where Countno = 1)
declare #Converttype varchar(max) = (select Converttype from #Converttype where Countno = 1)
declare #ColumnName varchar(max) = (select Column_Name from #ColumnName where Countno = 2)
declare #Iteration int = (select Count(COLUMN_NAME) from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'EXAMPLE')
declare #count int = 2
while #Count <= #Iteration
begin
--print #Count
set #CreateTable = #CreateTable+' varchar(max)' + ',' + (select Column_Name from #ColumnName where Countno = #count)
set #Converttype = #Converttype + ',' + (select Converttype from #Converttype where Countno = #count)
set #count = #count + 1
set #ColumnName = #ColumnName + ',' + isnull((select Column_Name from #ColumnName where Countno = #count),'')
end
declare #Unpivot nvarchar(max) = '
create table #temp (' + #CreateTable + ' varchar(max))
insert into #temp (ROWDATA,' + #ColumnName + ')
select ' + #Converttype + ' from EXAMPLE where ROWDATA = 2
select * from #temp
unpivot
(
ColumnValue
for ColumnName in (' + #ColumnName + ')
) AS Tablecheck'
Exec(#Unpivot)
After debugging I found out that #Unpivot is not working specially when I used print #Unpivot it doesn't show me the the message from select * from #temp to ) as Tablecheck

Answer 1

There is only a minor issue of the extra comma at the end of the #ColumnName otherwise your script works fine.
CREATE TABLE #ColumnName
(Countno INT IDENTITY(1, 1),
Column_Name VARCHAR(MAX)
);
INSERT INTO #ColumnName(Column_Name)
SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'EXAMPLE';
CREATE TABLE #Converttype
(Countno INT IDENTITY(1, 1),
Converttype VARCHAR(MAX)
);
INSERT INTO #Converttype(Converttype)
SELECT CASE
WHEN DATA_TYPE <> 'varchar'
THEN 'Cast(' + COLUMN_NAME + ' as varchar (max)) as ' + COLUMN_NAME
ELSE COLUMN_NAME
END
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'EXAMPLE';
DECLARE #CreateTable VARCHAR(MAX)=
(
SELECT Column_Name FROM #ColumnName WHERE Countno = 1
);
DECLARE #Converttype VARCHAR(MAX)=
(
SELECT Converttype FROM #Converttype WHERE Countno = 1
);
DECLARE #ColumnName VARCHAR(MAX)=
(
SELECT Column_Name FROM #ColumnName WHERE Countno = 2
);
DECLARE #Iteration INT=
(
SELECT COUNT(COLUMN_NAME) FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'EXAMPLE'
);
SELECT #Iteration
DECLARE #count INT= 2;
WHILE #Count <= #Iteration
BEGIN
print #Count
SET #CreateTable = #CreateTable + ' varchar(max)' + ',' +
(
SELECT Column_Name FROM #ColumnName WHERE Countno = #count
);
SET #Converttype = #Converttype + ',' +
(
SELECT Converttype FROM #Converttype WHERE Countno = #count
);
SET #count = #count + 1;
SET #ColumnName = #ColumnName + ',' + ISNULL(
(
SELECT Column_Name FROM #ColumnName WHERE Countno = #count
), '');
END;
DECLARE #Unpivot NVARCHAR(MAX)= '
create table #temp (' + #CreateTable + ' varchar(max))
insert into #temp (ROWDATA,' + SUBSTRING(#ColumnName, 1, LEN(#COLUMNNAME) - 1) + ')
select ' + #Converttype + ' from EXAMPLE where ROWDATA >= 2
select * from #temp
unpivot
(
ColumnValue
for ColumnName in (' + SUBSTRING(#ColumnName, 1, LEN(#COLUMNNAME) - 1) + ')
) AS Tablecheck';
print (#unpivot)
EXEC (#Unpivot);
Please see the db<>fiddle here.