Question

Using SQL Server 2005

Leave Table

ID StartDate EndDate 

001 04/01/2010 04/02/2010
002 04/02/2010 04/03/2010
…

Event Table

ID Date PresentDate Status

001 03/30/2010 03/30/2010 Present
001 03/31/2010 null       absent
001 04/01/2010 null       Leave
001 04/02/2010 null       Leave
001 04/03/2010 null       absent
001 04/04/2010 04/04/2010 Present
….

All the Datecolumn datatype is datetime

In the Status Column, if Present Date is null then it will display as “absent”, if not null then it will display as “present”. Now if we apply a leave for the date then it will display as “Leave” in status column.

Query

Select 
    id, date, present date
    , CASE WHEN t2.id IS NULL THEN t1.Status ELSE ‘Leave’ END AS status 
from event table as t1 
left outer join leave table as t2 on 
    t1.id = t2.id and t1.date between t2.startdate and t2.enddate

The above method is working, but I need to add one more condition.

Once if we applied the leave for the particular employee in the Leave Table then it should compare the Present Date column, if Present Date Column is empty then it should display as “leave”

Expected Output

ID Date PresentDate Status

001 03/30/2010 03/30/2010 Present
001 03/31/2010 null       absent
001 04/01/2010 null       Leave
001 04/02/2010 null       Leave
001 04/03/2010 null       Leave (Expect this value)
001 04/04/2010 04/04/2010 Present
….

From the above output Leave is starting from 04/01/2010 to 04/02/2010, then next column of present date is null then status should display as a “Leave”, once present date is not null then it should display as “Present.

Method

We can display as "Leave" in status column from Start Date to end date of leave table, after that leave date end then we can compare with PresentDate column, if PresentDate column is null then it should display as "Leave", once data is available in present column then status should display with normal condition.

How to make a query for the above condition.

Need Query Help

Answer 1

select E.id, E.date, E.presentdate, *,
    case
    when E.presentdate is not null then 'Present'
    when E2.presentdate is not null then 'Absent'
    when L.ID is not null then 'Leave'
    else 'Absent'
    end
from Event E
outer apply (
    select top 1 *
    from Leave L
    where E.presentdate is null and E.date >= L.startdate
      AND e.ID = L.ID
    order by L.startDate desc) L
outer apply (
    select top 1 *
    from Event E2
    where E.presentdate is null
      and E2.presentdate is not null
      and E.date >= E2.date and E2.date > L.startdate      
      AND e2.ID = e.ID
    order by E2.presentdate desc) E2
order by E.date

Leave table

ID          StartDate               EndDate
----------- ----------------------- -----------------------
1           2010-04-01 00:00:00.000 2010-04-02 00:00:00.000
1           2010-04-02 00:00:00.000 2010-04-03 00:00:00.000
1           2010-04-05 00:00:00.000 2010-04-05 00:00:00.000

Output

id          date                    presentdate             
----------- ----------------------- ----------------------- -------
1           2010-03-30 00:00:00.000 2010-03-30 00:00:00.000 Present
1           2010-03-31 00:00:00.000 NULL                    Absent
1           2010-04-01 00:00:00.000 NULL                    Leave
1           2010-04-02 00:00:00.000 NULL                    Leave
1           2010-04-03 00:00:00.000 NULL                    Leave -**
1           2010-04-04 00:00:00.000 2010-04-04 00:00:00.000 Present
1           2010-04-05 00:00:00.000 NULL                    Leave
1           2010-04-06 00:00:00.000 NULL                    Leave -**
1           2010-04-07 00:00:00.000 NULL                    Leave -**
1           2010-04-08 00:00:00.000 2010-04-08 00:00:00.000 Present
1           2010-04-09 00:00:00.000 NULL                    Absent
1           2010-04-10 00:00:00.000 NULL                    Absent
1           2010-04-11 00:00:00.000 2010-04-11 00:00:00.000 Present

The ones marked -** are not covered by Leave records, but they show leave because they follow a Leave period, correct? 2010-04-09 for example remains “Absent” because it follows a Present record (without actually being present).