Syntax Error when trying to use Dynamic Pivot Query - sql

Question

I've been playing around with the PIVOT function for a while. I have a table that looks like this
IdPersona IdEstadoSocio Periodo
-------------------------------
1044659 6 2021-06
721396 5 2021-06
219886 6 2021-06
1906611 7 2021-06
1027906 2 2021-06
Every ClientID is repeated once for each month. Every month new rows are added to the table with a new period associated to the row. It's an incrementing table.
What I need to do is to PIVOT the table, so that it basically ends up like this:
IdPersona 2021-01 2021-02 2021-03 2021-04
----------------------------------------
1044659 6 3 1 4
721396 5 5 2 6
219886 6 6 4 1
1906611 7 7 9 2
1027906 2 1 1 1
Naturally, I want my code to be dynamic. I don't want to harcode every month like:
SELECT *
FROM [fid].[FACT_Socios_Resumen_Periodo]
PIVOT(MAX(IdEstadoSocio)
FOR [Periodo] IN ([2021-01], [2021-02], [2021-03], [2021-04], [2021-05], [2021-06])) AS PVTTable
So I've been trying several dynamic solutions found in here, but none of them are working for me, and I don't know why. And it's driving me crazy.
This solutions gives me
Incorrect Syntax near 'FOR'
My code below:
DECLARE #cols AS NVARCHAR(MAX),#query AS NVARCHAR(MAX);
SET #cols = STUFF((SELECT DISTINCT ',' + QUOTENAME(periodo)
FROM [fid].[FACT_Socios_Resumen_Periodo]
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT IdPersona, ' + #cols + ' from
(
select IdPersona
, IdEstadoSocio
, periodo
from [fid].[FACT_Socios_Resumen_Periodo]
) x
pivot
(
max(IdEstadoSocio)
for periodo in (' + #cols + ')
) p '
execute(#query)
The second solution provided in the same link gives me
A variable that has been assigned in a SELECT statement cannot be
included in a expression or assignment when used in conjunction with a
from clause.
Which is kinda understandable, as the query tries to solve getting the DISTINCT values of [Period] in a recursive way, as far as I understood. However, everybody accepted that as a viable answer too.
My code below:
DECLARE #cols AS NVARCHAR(MAX)='';
DECLARE #query AS NVARCHAR(MAX)='';
SELECT #cols = #cols + QUOTENAME(periodo) + ',' FROM (select distinct periodo from [fid].[FACT_Socios_Resumen_Periodo] ) as tmp
select #cols = substring(#cols, 0, len(#cols)) --trim "," at end
set #query =
'SELECT * from
(
select idpersona, idestadosocio, periodo from [fid].[FACT_Socios_Resumen_Periodo]
) src
pivot
(
max(idestadosocio) for periodo in (' + #cols + ')
) piv'
execute(#query)
The third solution I tried gives me the same error noted above, with a similar syntax but not exactly the same. It tries to solve the DISTINCT [Period]s recursively.
My code below:
DECLARE #DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE #ColumnName AS NVARCHAR(MAX)
--Get distinct values of the PIVOT Column
SELECT #ColumnName = ISNULL(#ColumnName + ',', '') + QUOTENAME(periodo)
FROM (SELECT DISTINCT periodo FROM [fid].[FACT_Socios_Resumen_Periodo]) AS Periodos
--Prepare the PIVOT query using the dynamic
SET #DynamicPivotQuery =
N'SELECT IdPersona, ' + #ColumnName + '
FROM [fid].[FACT_Socios_Resumen_Periodo]
PIVOT(MAX(IdEstadoSocio)
FOR periodo IN (' + #ColumnName + ')) AS PVTTable'
--Execute the Dynamic Pivot Query
EXEC sp_executesql #DynamicPivotQuery
So, what exactly am I doing wrong?? Can anybody throw me a hint? I'm failing over solutions approved by the whole community, and I can't understand why. I basically tried to understand the code, copied it, and replaced columns and tables. Just that. I didn't change anything more. Thanks in advance!

Answer 1

Looking at your third solution.
First thing I notice is that you are not coalescing the initial null value of #ColumnName when you do your concatenation.
SELECT #ColumnName = Isnull(#ColumnName + ',', '') + QUOTENAME(periodo)
FROM (SELECT DISTINCT periodo FROM [fid].[FACT_Socios_Resumen_Periodo]) AS Periodos
That should solve your problem.
If you would PRINT the result #ColumnName and #DynamicPivotQuery, before you execute it, it will usually show you where the problems are.
For versions of sql that do not support SELECT #Variable
SQL Azure and SQL DW only support using SET when setting variable values.
You can use STRING_AGG() on these servers
set #ColumnName = (select string_agg(QUOTENAME(periodo),',') from (select distinct periodo from FACT_Socios_Resumen_Periodo) t)