Question

PL/SQL select max(date)

Asked by: cookiejar

I am using select max(date) in a subquery and it is taking a while to return the results of the query.  The amount of records that is being return are approximately 17,000 records.  Is there another alternative to using select(max) to get the latest date for a user set of records that would speed up performance.

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Asked On
2009-07-23 at 08:51:19ID24595095
Topic

PL / SQL

Participating Experts
4
Points
500
Comments
7

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Answers

 

by: pssandhuPosted on 2009-07-23 at 09:01:43ID: 24926734

That would be best way I am afraid. Can you post your query so we can look to see if we can make any changes to speed things up?

P.

 

by: ravindran_eeePosted on 2009-07-23 at 09:02:31ID: 24926750

Attempting to do anything else (like sorting and selecting the record with rank 1) would result in the same execution time (or worse!!). I think we will have to settle with MAX only

 

by: angelIIIPosted on 2009-07-23 at 09:03:22ID: 24926762

yes.
you can use the ROW_NUMBER() function to return the # , and filter by that.

select * 
from  (
   select field1, date, row_number() over (partition by field1 order by date desc ) r
    from yourtable
 ) sq
where sq.r = 1

                                              
1:
2:
3:
4:
5:
6:

Select allOpen in new window

 

by: HainKurtPosted on 2009-07-23 at 09:32:22ID: 24927133

you should add and index on the date field, it will be faster

 

by: cookiejarPosted on 2009-07-23 at 09:36:40ID: 24927178

This is a sample of my query:

SELECT master_lectures.etl_lecture_id,
            master_tasklist_versions.name lecture_list,
            lecture_versions.title,
            lecture_types.name lecture_type,
            get_department (p.emp_id) department,
            get_emp_name (p.emp_id) emp_name,
            ethic_group_lectures.completion_date,
            ethic_group_lectures.hours,
            ethic_group_lectures.instructor_name,
            ethic_group_lectures.expiration_date,
            ethic_group_lectures.notification_date,
            DECODE (
               (ethic_group_lectures.expiration_date - SYSDATE)
               - ABS (ethic_group_lectures.expiration_date - SYSDATE),
               0,
               'CURRENT',
               'EXPIRED'
            )
               status
     FROM   ethic_group_lectures,
            ethic_lectures,
            lecture_versions,
            master_lectures,
            master_tasklist_versions,
            master_tasks,
            master_tasklist_types,
            lecture_types,
            people p,
            people_assignments pa,
            department
    WHERE   master_tasklist_types.name = 'LECTURE LIST'
            AND ethic_group_lectures.itl_group_lecture_id =
                  ethic_lectures.itl_group_lecture_id
            AND lecture_versions.etl_lecture_version_id =
                  ethic_group_lectures.etl_lecture_version_id
            AND lecture_versions.ndm_lecture_type_id =
                  lecture_types.ndm_lecture_type_id
            AND lecture_versions.etl_lecture_version_id =
                  master_lectures.current_version_id
            AND lecture_versions.etl_lecture_version_id =
                  master_lectures.production_version_id
            AND master_lectures.etl_lecture_id =
                  lecture_versions.etl_lecture_id
            AND p.emp_id = ethic_lectures.emp_id
            AND ethic_group_lectures.department_id =
                  department.department_id
            AND p.emp_id = pa.emp_id
            AND ( (p.checked_in_reporting_id = pa.per_assignment_id
                   AND pa.department_id =
                         ethic_group_lectures.department_id)
                 OR (p.orders_to_assign_id = pa.per_assignment_id
                     AND pa.department_id =
                           ethic_group_lectures.department_id))
            AND master_tasks.etl_task_target_id = master_lectures.etl_lecture_id
            AND master_tasklist_versions.ndm_tasklist_type_id =
                  master_tasklist_types.ndm_tasklist_type_id
            AND master_tasklist_versions.etl_tasklist_version_id =
                  master_tasks.etl_tasklist_version_id
            AND ethic_group_lectures.completion_date =
                  (SELECT   MAX (el.completion_date)
                     FROM   ethic_group_lectures el,
                            ethic_lectures etl,
                            lecture_versions lv,
                            master_lectures etl_l
                    WHERE   el.itl_group_lecture_id =
                               etl.itl_group_lecture_id
                            AND el.etl_lecture_version_id =
                                  lv.etl_lecture_version_id
                            AND lv.etl_lecture_id = etl_l.etl_lecture_id
                            AND etl.emp_id = p.emp_id
                            AND etl_l.etl_lecture_id =
                                  master_lectures.etl_lecture_id)

 

by: angelIIIPosted on 2009-08-16 at 03:52:35ID: 25108508

cookiejar,
 did you try my suggestion from http://#a24926762 ?

 

by: angelIIIPosted on 2009-08-16 at 03:52:54ID: 25108509

also, can you show the explain plan for your query?

20120131-EE-VQP-002

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