Question

In MSSQL 2008 I have table and data which looks like this

create table #tempData
(user_id int,type varchar(10),ts datetime)

insert into #tempData
select 1,'ENTER','2011-01-30 15:00:00'
union all
select 1,'EXIT','2011-01-31 16:00:00'
union all
select 1,'ENTER','2011-02-1 18:00:00'
union all
select 1,'EXIT','2011-02-10 21:00:00'
union all
select 2,'ENTER','2011-01-10 21:00:00'
union all
select 2,'EXIT','2011-01-12 21:00:00'
union all
select 2,'ENTER','2011-01-13 01:00:00'
union all
select 2,'EXIT','2011-01-13 18:00:00'
--AND SO ON --

Now I trying to make query which is going to tell how long one user was inside according to last exit
something like

user_id,exited,time_in_hours
1,'2011-01-31 16:00:00',25 
1,'2011-02-10 21:00:00',219
2,'2011-01-12 21:00:00',48
2,'2011-01-13 18:00:00',17

Sorry if this BAD or ROUGE question and if this is not proper way to ask a question like this.
But I am stacked on this for while.

Answer 1

Assuming that

• same-user sessions do not intersect,

• there cannot be an EXIT record without the corresponding ENTER record,

you could try the following:

WITH ranked AS (
  SELECT
    user_id,
    type,
    ts,
    rn = ROW_NUMBER() OVER (PARTITION BY user_id, type ORDER BY ts)
  FROM #tempData
)
SELECT
  tx.user_id,
  exited = tx.ts,
  hours = DATEDIFF(HOUR, tn.ts, tx.ts)
FROM ranked tn
  INNER JOIN ranked tx ON tn.user_id = tx.user_id AND tn.rn = tx.rn
WHERE tn.type = 'ENTER'
  AND tx.type = 'EXIT'