Question

I’ve been asked to look at a database that records user login and logout activity – there’s a column for login time and then another column to record logout, both in OLE format. I need to pull together some information about user concurrency – i.e. how many users were logged in at the same time each day.

Do anyone know how to do this in SQL? I don’t really need to know the detail, just the count per day.

Thanks in advance.

Answer 1

I think this will work.

Select C.Day, Max(C.Concurrency) as MostConcurrentUsersByDay
FROM 
(
   SELECT convert(varchar(10),L1.StartTime,101) as day, count(*) as Concurrency
   FROM login_table L1
   INNER JOIN login_table L2 
      ON (L2.StartTime>=L1.StartTime AND L2.StartTime<=L1.EndTime) OR
         (L2.EndTime>=L1.StartTime AND L2.EndTime<=L1.EndTime)
    WHERE (L1.EndTime is not null) and L2.EndTime Is not null)  AND (L1.ID<>L2.ID)
    GROUP BY convert(varchar(10),L1.StartTime,101)
) as C    
Group BY C.Day