t-sql - compute the difference between dates for each row

Question

Can you show how can this be done in t-sql?

sample records

accountnumber trandate
-------------------------
1000          02-11-2010
1000          02-12-2010
1000          02-13-2010
2000          02-10-2010
2000          02-15-2010

How to compute the # of days between each transactions for each accountnumber? like this

accountnumber trandate       # of days
----------------------------------------
1000          02-11-2010       0
1000          02-12-2010       1
1000          02-13-2010       1
2000          02-10-2010       0
2000          02-15-2010       5

Thanks a lot!

Answer 1

you can use between and

select * from table1 where trandate  between 'date1' and 'date2'

Answer 2

SELECT accountnumber, 
       trandate, 
       Datediff(DAY, a.trandate, (SELECT TOP 1 trandate 
                                  FROM   mytable b 
                                  WHERE  b.trandate > a.trandate 
                                  ORDER  BY trandate)) 
FROM   mytable a 
ORDER  BY trandate 

Answer 3

Hope this helps.

Select A.AccountNo, A.TranDate, B.TranDate as PreviousTranDate, A.TranDate - B.Trandate as NoOfDays
from
(Select AccountNo, TranDate, Row_Number() as RNO over (Partition by AccountNo order by TranDate)) as A, 
(Select AccountNo, TranDate, Row_Number() as RNO over (Partition by AccountNo order by TranDate)) as B
Where A.AccountNo = B.AccountNo and A.RNO -1  = B.RNO

You can also use a CTE expression to increase preformance.