Error Invalid Use Of Side-effecting Or Time-dependent Operator In 'EXECUTE STRING' Within A Function

Hi all, mister
I want create a function but I get this error: Error Invalid use of side-effecting or time-dependent operator in 'EXECUTE STRING' within a function

I think in a function, cannot use temp tables, or calling exec or store procedures.

Which is the best solution for my issue ? develop store procedure ??

thanks.

CREATE FUNCTION fnObtenerTablaMaestra ()

RETURNS @T Table ( Descripcion VARCHAR(20) NOT NULL, CIF VARCHAR(8) NULL )

AS

BEGIN

DECLARE @cmd nvarchar(max)

DECLARE @sql nvarchar(max)

DECLARE @nexoUNION NVARCHAR(max)

DECLARE @params nvarchar(max)

DECLARE @NombreTabla VARCHAR(MAX)

DECLARE @Descripcion VARCHAR(MAX)

DECLARE @CIF VARCHAR(MAX)

-- Cannot access temporary tables from within a function.

-- IF EXISTS (SELECT TABLE_NAME FROM tempdb.INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME LIKE '#tmpTable%')

-- DROP TABLE #tmpTable

-- CREATE TABLE #tmpTable ( Descripcion VARCHAR(20) NOT NULL, CIF VARCHAR(8) NULL )



SET @nexoUNION = NULL



DECLARE c1 CURSOR for

SELECT [CD_NOMBRE_TABLA], [DS_CAMPO_DESCRIPCION], [DS_CAMPO_CIF] FROM [TABLA_MAESTRA]



OPEN c1

FETCH c1 INTO @NombreTabla, @Descripcion, @CIF

--FETCH NEXT FROM c1 INTO @NombreTabla, @Descripcion, @CIF

WHILE @@FETCH_STATUS >= 0

--WHILE @@FETCH_STATUS = 0

BEGIN

SELECT @sql =

'INSERT INTO #tmpTable

N'''+ @NombreTabla + '''

N'''+ @Descripcion + '''

N'''+ @CIF + ''''



SELECT @sql =

'SELECT ' + @Descripcion + ', '+ @CIF + ' FROM ' + @NombreTabla

IF @nexoUNION IS NULL

BEGIN

SET @nexoUNION = 'UNION'

END

ELSE

SET @sql = @nexoUNION + ' ' + @sql



-- EXECUTE (@sql)

--Exec(@sql)

FETCH c1 INTO @NombreTabla, @Descripcion, @CIF

--FETCH NEXT FROM c1 INTO @NombreTabla, @Descripcion, @CIF



END

CLOSE c1

DEALLOCATE c1

--SET @sql = 'SELECT Descripcion, CIF FROM #tmpTable'

-- Error Invalid use of side-effecting or time-dependent operator in 'EXECUTE STRING' within a function

EXECUTE(@sql)

RETURN

END

GO