Tuning SQL query

Question

Please help me in tuning this query. This view has around 2 million of records
SELECT * FROM employee_v
WHERE status_id IN (SELECT MAX(v2.status_id)status_id
FROM employee_v v2
WHERE UPPER(v2.name) LIKE UPPER(:v_name)||'%'
GROUP BY v2.emp_id, v2.project_id)
ORDER BY status_type_id;
Here:
employees may work on one or more projects
employee working on a given project may have one or more status_ids associated.
for example:
emp_id     project_id     status_id
10     100     1
10     100     2
20     100     2
20     200     3
30     100     4
30     200     5
30     200     6
40     200     6
If you have any other suggestions , please let me know too. For example, I was thinking that the subquery should use actual tables instead of the view because view is based on 10 tables and the subquery can instead use two tables . Does it make sense?
Thanks a lot for the help!
Edited by: user5406804 on Apr 20, 2010 5:42 AM

Answer 1

If you have any other suggestions , please let me know too. Wild shot in the dark, but maybe using EXISTS instead of IN speeds up your query:
untested for obvious reasons
select *
from  employee_v v
where  upper(v.name) like upper(:v_name)||'%'
where not exists ( select null
                   from   employee_v v2
                   and    v2.status_id > v.status_id                  
                   and    v2.emp_id = v.emp_id -- assuming you have some emp_id PK column
                                               -- if necessary, you need to change the name of this column ofcourse
order by status_type_id;Do compare the resultsets, not sure this will give you the same/desired result, but it might give you an idea.
For example, I was thinking that the subquery should use actual tables instead of the view because > view is based on 10 tables and the subquery can instead
use two tables . Does it make sense?Sounds like worth a try to me, yes. Less data to plough through = faster response.
As well as using a function based index on UPPER(name) might be worth a try.