Query per convertire Varchar HH:MM in minuti interi in SQL Server 2008

Prova

SELECT LTRIM(DATEDIFF(MINUTE, 0, TimeSpent)) 
  FROM yourtable

Dato

| TIMESPENT |
-------------
|     00:12 |
|     01:05 |
|     10:00 |

Uscita:

| MINUTES |
-----------
|      12 |
|      65 |
|     600 |

Ecco SQLFiddle