USE tempdb;

CREATE TABLE dbo.Flussi(
ID int IDENTITY(1,1) NOT NULL,
Tipo char(1) NULL,
Descrizione varchar(20) NULL,
Mese int NULL,
Importo decimal(5, 2) NULL
);

INSERT dbo.Flussi VALUES
      ('C','Rimborso',2,200)
    , ('C','Rimborso',5,200)
    , ('C','Rimborso',3,100)
    , ('C','Rimborso',4,230)
    , ('C','Fattura passiva',1,100)
    , ('C','Fattura passiva',2,400)
    , ('C','Fattura passiva',5,200)
    , ('C','Fattura passiva',6,140)
    , ('C','Fattura passiva',4,90)
    , ('C','Personale',4,100)
    , ('C','Personale',1,120);

WITH CTE_PIVOT AS
(
    SELECT
          P.Descrizione
        , [1], [2], [3], [4], [5], [6]
        , [7], [8], [9], [10], [11], [12]
      
    FROM dbo.Flussi AS F
    PIVOT (
        MAX(Importo)
        FOR Mese IN(
            [1], [2], [3], [4], [5], [6]
          , [7], [8], [9], [10], [11], [12]
        )
    ) AS P
)
SELECT 
      Descrizione
    , MAX(COALESCE([1], 0)) AS [1]
    , MAX(COALESCE([2], 0)) AS [2]
    , MAX(COALESCE([3], 0)) AS [3]
    , MAX(COALESCE([4], 0)) AS [4]
    , MAX(COALESCE([5], 0)) AS [5]
    , MAX(COALESCE([6], 0)) AS [6]
    , MAX(COALESCE([7], 0)) AS [7]
    , MAX(COALESCE([8], 0)) AS [8]
    , MAX(COALESCE([9], 0)) AS [9]
    , MAX(COALESCE([10], 0)) AS [10]
    , MAX(COALESCE([11], 0)) AS [11]
    , MAX(COALESCE([12], 0)) AS [12]
FROM CTE_PIVOT
GROUP BY Descrizione;

/* Output:

Descrizione          1       2       3       4       5       6       7     8     9     10    11    12
-------------------- ------- ------- ------- ------- ------- ------- ----- ----- ----- ----- ----- -----
Fattura passiva      100.00  400.00  0.00    90.00   200.00  140.00  0.00  0.00  0.00  0.00  0.00  0.00
Personale            120.00  0.00    0.00    100.00  0.00    0.00    0.00  0.00  0.00  0.00  0.00  0.00
Rimborso             0.00    200.00  100.00  230.00  200.00  0.00    0.00  0.00  0.00  0.00  0.00  0.00

(3 row(s) affected)

*/

DROP TABLE dbo.Flussi;