我有下表:
ticket arrivaltime resolution time status
t1 '2012-09-03' null new
t2 '2012-09-04' null new
t1 (can be anything) '2012-09-14' verified
t1 (can be anything) '2012-09-16' verified
t2 (can be anything) '2012-09-06' verified
例如,现在我想找到 t1 的天数差异:
Age(t1)=(resolution time of last entry) - (arrival time of first entry)
同样,我会为 t2 找到它。
我怎样才能找到这个?