SQL Query using Subquery to get the difference in budget versions

Question

Hi
I am using the following query to find the difference between revenue budget changes from the previous version to latest version. However the second subquery is not working. Has somebody done a similar query before? Any help?
select distinct b.name, b.segment1, a.version_number , a.version_name, a.change_reason_code, a.revenue, f.revenue, a.creation_date, d.full_name
from PA_BUDGET_VERSIONS a, pa_projects_all b, fnd_user c, per_all_people_f d,PA_BUDGET_VERSIONS f
where a.project_id = b.project_id
and a.created_by = c.user_id
and c.employee_id = d.person_id
and a.budget_type_code = 'AR'
and a.budget_status_code = 'B'
and b.org_id in (147,707,140)
and a.version_number in (select max(e.version_number) from PA_BUDGET_VERSIONS e where e.budget_version_id = a.budget_version_id
and a.project_id = e.project_id)
and a.budget_version_id = f.budget_version_id
and f.version_number in (Select max(g.version_number) from PA_BUDGET_VERSIONS g where f.budget_version_id = g.budget_version_id
and f.project_id = g.project_id and g.version_number < a.version_number)
and a.creation_date between '01-JAN-09' and '30-JAN-09'
order by b.segment1;

Answer 1

Analytic functions to the rescue! (Now you'll only have one pass through the pa_budget_version table, instead of four!)
Something like this, perhaps (assuming version_numbers are unique per project_id and budget_version_id):
WITH a AS (SELECT project_id,
                  version_number,
                  version_name,
                  change_reason_code,
                  creation_date,
                  revenue,
                  row_number() over (partition by project_id, budget_version_id
                                     order by version_number desc) rn,
                  lag(revenue) over (partition by project_id, budget_version_id
                                     order by version_number desc) prev_ver_revenue
           FROM   pa_budget_versions
           WHERE  budget_type_code = 'AR'
           AND    budget_status_code = 'B'
           AND    creation_date BETWEEN to_date('01/01/2009', 'dd/mm/yyyy')
                                AND     to_date('30/01/2009', 'dd/mm/yyyy'))
SELECT DISTINCT b.name,
                b.segment1,
                a.version_number,
                a.version_name,
                a.change_reason_code,
                a.revenue,
                a.prev_ver_revenue,
                a.creation_date,
                d.full_name
FROM   a,
       pa_projects_all b,
       fnd_user c,
       per_all_people_f d
WHERE  a.project_id = b.project_id
AND    a.created_by = c.user_id
AND    c.employee_id = d.person_id
AND    b.org_id IN (147, 707, 140)
ORDER BY b.segment1;NB. untested.