Chaning varchar Meridiem Time to Twenty Four Hour time in Sql

I have this type of data

alt text http://img46.imageshack.us/img46/6351/timed.png

TimeOFD开发者_如何学运维ay column is varchar. I want to change this time in 24 hour time, using SQL, and updating TwentyFourHourTime column. TwentyFourHourTime column is also varchar.

How can I do this.

Thanks.

i've written this test - seems to work. works with midnight and adding a leading zero.

UPDATED:

DROP TABLE #times

CREATE TABLE #times
(
    TimeOfDay  VARCHAR(32),
    TimeMeridiem VARCHAR(32),
    TwentyFourHourTime VARCHAR(32)
)

INSERT INTO #times (TimeOfDay, TimeMeridiem) VALUES ('1:00', 'PM')
INSERT INTO #times (TimeOfDay, TimeMeridiem) VALUES ('1:00', 'AM')
INSERT INTO #times (TimeOfDay, TimeMeridiem) VALUES ('12:00', 'PM')

UPDATE #times SET TwentyFourHourTime = REPLACE(Right(Replicate('0',5) +
REPLACE((SELECT CASE WHEN TimeMeridiem = 'PM' THEN
CAST((SELECT REPLACE(TimeOfDay,':','.')) AS dec(10,2)) + 12 ELSE 
(SELECT REPLACE(TimeOfDay,':','.')) END), '24.', '00.') ,5), '.', ':')

SELECT * FROM #times

RESULT:

TimeOfDay TimeMeridiem TwentyFourHourTime 
--------- ------------ ------------------ 
1:00      PM           13:00              
1:00      AM           01:00              
12:00     PM           00:00  

try the following query:

update tableName set  TwentyFourHourTime =
case TimeMeridiem 
WHEN 'PM' THEN Convert(varchar,dateadd(hour,12,TimeOFDay),108)
 ELSE Convert(varchar,TimeOFDay,108)
end