try these..
SELECT
Sum(DateDiff(minute, 0, Opt)) As [TotalMinutes],
Convert(varchar(5), Sum(DateDiff(minute, 0, Opt)+1) / 60)
+ ' hours '
+ Convert(char(2), Sum(DateDiff(minute, 0, Opt)+1) % 60)
+ ' minutes'
As [Description]
FROM
time_table
Updated..It's bad idea,you better see @Richard Deeming solution
SELECT
Sum(DateDiff(minute, 0, Opt)) As [TotalMinutes],
case when Opt='23:59' then
Convert(varchar(5), Sum(DateDiff(minute, 0, Opt)+1) / 60)
+ ' hours '
+ Convert(char(2), Sum(DateDiff(minute, 0, Opt)+1) % 60)
+ ' minutes'
else
Convert(varchar(5), Sum(DateDiff(minute, 0, Opt)) / 60)
+ ' hours '
+ Convert(char(2), Sum(DateDiff(minute, 0, Opt)) % 60)
+ ' minutes'
end
As [Description]
FROM
time_table group by Opt