Question

I have a table with fields username and a lastUpdateDateTime. If the user makes more than one entry into this table I would like to see what the difference is between the first and last entry is in minutes and seconds. I thought I might use the function DATEDIFF but my database does not have a start date and end date as two separate fields. Should I use a cursor to loop the results ordered by username?

Not sure how to do this.

HERE IS THE LATEST…

SELECT username,  
DATEDIFF(ss, MinDate, MaxDate) Assessment_Timespan,
AssessmentDate
FROM
(
SELECT storeID, username,
MIN(lastUpdateDateTime) MinDate,
MAX(lastUpdateDateTime) MaxDate, 
CONVERT(VARCHAR(50), LastUpdateDateTime, 101) AS AssessmentDate
FROM Assessment
GROUP BY username, storeID, CONVERT(VARCHAR(50), LastUpdateDateTime, 101)
) src

Answer 1

You could use something like this. Which gets both the min and max value for each username. Once you have that, then you can apply the DateDiff() function to it:

select username,  
  datediff(ss, MinDate, MaxDate) DiffInSeconds
from
(
  select username,
    min(lastUpdateDateTime) MinDate,
    max(lastUpdateDateTime) MaxDate
  from yourtable
  group by username
) src

See SQL Fiddle with Demo

This gives you the difference in seconds, you can then format it in any manner that you need.