Question

Given this table:

How can I get the datediff in days between each status_date for each group of ID_Number? In other words I need to find the number of elapsed days for each status that the ID_Number has been given.

Some things to know:

• All ID_Number will have a received_date which should be the earliest date for each ID_Number (but app doesn’t enforce)
• For each ID_Number there will be a status with a corresponding status_date which is the date that the ID_Number was given that particular status.
• The status column doesn’t always necessarily go in the same order every time (app doesn’t enforce)
• All ID_Number will have a closed_date which should be the latest date (but app doesn’t enforce)

Sample output:
So for ID_Number 2001, the first date (received_date) is 2009-05-02 and the next date you encounter has a status of ‘open’ and is 2009-05-02 so elapsed days is 0. Moving on to the next date encountered is 2009-05-10 with a status of ‘invest’ and the elapsed days is 8 counting from the prior date. The next date encountered is 2009-07-11 and the elapsed days is 62 counting from the previous date.

Edited to add:

Is it possible to have the elapsed days end up as a column on this table/view?
I also forgot to add that this is SQL Server 2000.

Answer 1

What I understand is that you need the difference between the first status_date and the next status_date for the same id and so on up to the closed_date.

This will only work in SQL 2005 and up.

;with test as (
    select 
        key,
        id_number,
        status,
        received_date,
        status_date,
        closed_date,
        row_number() over (partition by id order by status_date, key ) as rownum
    from @test
    )
select 
    t1.key,
    t1.id_number,
    t1.status,
    t1.status_date,
    t1.received_date,
    t1.closed_date,
    datediff(d, case when t1.rownum = 1 
                then t1.received_date
                else    
                    case when t2.status_date is null 
                        then t1.closed_date 
                        else t2.status_date 
                    end
            end,
            t1.status_date
         ) as days
from test t1
left outer join test t2
on t1.id = t2.id
    and t2.rownum = t1.rownum - 1

This solution will work with SQL 2000 but I am not sure how good will perform:

select *,
    datediff(d,
        case when prev_date is null
            then closed_date
            else prev_date
        end,
        status_date )
from ( 
    select *,
        isnull( ( select top 1 t2.status_date 
          from @test t2
          where t1.id_number = t2.id_number
            and t2.status_date < t1.status_date
          order by t2.status_date desc
          ),received_date) as prev_date 
    from @test t1
) a
order by id_number, status_date

Note: Replace the @Test table with the name of your table.