Confronto fra date e conversione in datetime

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USE tempdb;
GO

CREATE TABLE dbo.myDates(
DateID int NOT NULL IDENTITY PRIMARY KEY,
Anno int NOT NULL,
Mese int NOT NULL,
Giorno int NOT NULL,
Ora int NOT NULL,
Minuti int NOT NULL
);
GO

INSERT dbo.myDates VALUES(1971, 6, 12, 12, 5);
INSERT dbo.myDates VALUES(2006, 5, 11, 15, 2);
INSERT dbo.myDates VALUES(1943, 11, 3, 8, 32);
GO

WITH myCTE (myDate) AS
(
  SELECT
      CAST(Anno AS char(4)) +                             -- Anno
      RIGHT('00' + CAST(Mese AS varchar(2)), 2) +         -- Mese
      RIGHT('00' + CAST(Giorno AS varchar(2)), 2) + ' ' + -- Giorno
      RIGHT('00' + CAST(Ora AS varchar(2)), 2) + ':' +    -- Ora
      RIGHT('00' + CAST(Minuti AS varchar(2)), 2)         -- Minuti
  FROM dbo.myDates
)
SELECT 
      myDate
    , CAST(myDate AS smalldatetime) AS mySmalldatetime
    , DATEDIFF(day, myDate, CURRENT_TIMESTAMP) AS DiffDays
FROM myCTE;
GO

/* Output:

myDate         mySmalldatetime         DiffDays
-------------- ----------------------- -----------
19710612 12:05 1971-06-12 12:05:00     12752
20060511 15:02 2006-05-11 15:02:00     0
19431103 08:32 1943-11-03 08:32:00     22835

(3 row(s) affected)

*/

DROP TABLE dbo.myDates;