Get the Currently logged user and their last login time in SQL Server

Question

Here is my user log table

ID  USERID         TIME           TYPE
1    6             12:48:45       OUT
2    11            12:08:46       IN
3    6             12:18:45       IN
4    6             12:08:45       IN
5    9             12:06:44       IN
6    11            11:08:46       IN

I need get currently loggedin user and last logged in time in SQL Server . Output like this

ID  USERID          TIME           TYPE
2    11             12:08:46       IN
5    9              12:06:44       IN

Answer 1

The solution consists in using 2 CTEs, the first one contains all logged in users and the second contains all logged out users. Then the final select take those logged-in users that are not yet logged-out.

WITH loggedIn
AS
(
    SELECT userId, MAX([time]) LastLogIn
    FROM logtable
    WHERE [type]='IN'
    GROUP BY userId
),
loggedOut
AS
(
    SELECT userId, MAX([time]) LastLoginOut
    FROM logtable
    WHERE [type]='OUT'
    GROUP BY userId
)
SELECT loggedIn.userId, loggedIn.LastLogin
FROM loggedIn
WHERE
    userId NOT IN (SELECT userId FROM loggedOut)    
    --AND LastLogIn > @currentTime

Answer 2

Using your test data..

Declare @logintable table (id int, userid int, time datetime, type varchar(3))
Insert into @logintable values (1,6,'12:48:45','OUT')
Insert into @logintable values (2,11,'12:08:46','IN')
Insert into @logintable values (3,6,'12:18:45','IN')
Insert into @logintable values (4,6,'12:08:45','IN')
Insert into @logintable values (5,9,'12:06:44','IN')
Insert into @logintable values (6,11,'11:08:46','IN')

..this query should get you the result set you are after

SELECT
   a.* 
FROM 
   @logintable a 
INNER JOIN 
   (SELECT userid, MAX(time) as time FROM @logintable b GROUP BY userid) b
ON 
   a.userid = b.userid AND a.time = b.time
WHERE
   a.type = 'IN'
ORDER BY 
   a.id

The subquery finds the most recent entry for each user and compares it with the record we're currently looking at (that must be an 'IN' record). By doing this we automatically find logged in users.

Note that I have joined on MAX(TIME) here where it would be nicer to join on MAX(ID) - I would guess that in production your ID column would be sequential (ideally an identity column) and so the bigger the value of id the bigger the value of time .

The above query gives these results

ID  UserID Time                     Type
2   11     1900-01-01 12:08:46.000  IN
5   9      1900-01-01 12:06:44.000  IN