Solved

Optimization of nested queries

Posted on 2008-10-23
5
414 Views
Last Modified: 2013-12-18
Is there a more optimized way to wirte the below query, if yes how and why !

select e.DSORGUT as AGENCEDSORGUT, e.CDORGFNC as AGENCECDORGFNC, e.NOBRN as AGENCENOBRN,
            f.DSORGUT as AGENCEDSORGUT, f.CDORGFNC as AGENCECDORGFNC, f.NOBRN as AGENCENOBRN,
            g.DSORGUT as AGENCEDSORGUT, g.CDORGFNC as AGENCECDORGFNC, g.NOBRN as AGENCENOBRN
       from SYNOUP e, SYNOUP f, SYNOUP g
       where e.NOINP = (select b.NOINPREL from SYNRIP b, SYNREF c where b.NOINP = c.NOINP and b.CDRIC = 'A' and b.CDRIC IS NOT NULL )
       and f.NOINP = (select b.NOINPREL from SYNRIP b, SYNREF c where b.NOINP = c.NOINP and b.CDRIC = 'D' and b.CDRIC IS NOT NULL )
       and g.NOINP = (select b.NOINPREL from SYNRIP b, SYNREF c where b.NOINP = c.NOINP and b.CDRIC = 'R' and b.CDRIC IS NOT NULL )
0
Comment
Question by:gursheenz2008
  • 3
5 Comments
 
LVL 14

Expert Comment

by:GGuzdziol
Comment Utility

with adr as (

  select 

      max(case when b.CDRIC = 'A' THEN b.NOINPREL else null end) as noinprel_a, 

      max(case when b.CDRIC = 'D' THEN b.NOINPREL else null end) as noinprel_d, 

      max(case when b.CDRIC = 'R' THEN b.NOINPREL else null end) as noinprel_r, 

    from SYNRIP b, SYNREF c 

    where b.NOINP = c.NOINP and b.CDRIC in ('A', 'D', 'R') and b.CDRIC IS NOT NULL

)

select e.DSORGUT as AGENCEDSORGUT, e.CDORGFNC as AGENCECDORGFNC, e.NOBRN as AGENCENOBRN,

            f.DSORGUT as AGENCEDSORGUT, f.CDORGFNC as AGENCECDORGFNC, f.NOBRN as AGENCENOBRN,

            g.DSORGUT as AGENCEDSORGUT, g.CDORGFNC as AGENCECDORGFNC, g.NOBRN as AGENCENOBRN

       from SYNOUP e, SYNOUP f, SYNOUP g, adr

     where e.NOINP = adr.noinprel_a

       and f.NOINP = adr.noinprel_d

       and g.NOINP = adr.noinprel_r

Open in new window

0
 
LVL 14

Expert Comment

by:GGuzdziol
Comment Utility
This techinique is called "Subquery factoring".
0
 

Author Comment

by:gursheenz2008
Comment Utility
Thanks for this !

Please correct my understanding !

1.max(case when b.CDRIC = 'A' THEN b.NOINPREL else null end) as noinprel_a,
 This will take the MAX of NOINPREL if there's a value, else null value.

Why we again need b.CDRIC in ('A', 'D', 'R')?

2. "with"  Clause will treat the result of the query as a temp table(GTT)/ in line view.

3. This is not a PL/SQL block, it's a SQL statement

with adr as ( ... ) select ...
       and g.NOINP = adr.noinprel_r ;

4.When Oracel will drop this temp table(GTT)/ in line view.
0
 
LVL 73

Expert Comment

by:sdstuber
Comment Utility
is noinp a unique key for synoup?
0
 
LVL 14

Accepted Solution

by:
GGuzdziol earned 250 total points
Comment Utility
1. It may make Oracle uses index on that field.
2&4. Results of the query will be put in temporary table in temporary tablespace. Once query is finished space may be reused by other processes.
3. Yes, it's SQL statement: http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_10002.htm#i2077142
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Join & Write a Comment

Working with Network Access Control Lists in Oracle 11g (part 1) Part 2: http://www.e-e.com/A_9074.html So, you upgraded to a shiny new 11g database and all of a sudden every program that used UTL_MAIL, UTL_SMTP, UTL_TCP, UTL_HTTP or any oth…
Using SQL Scripts we can save all the SQL queries as files that we use very frequently on our database later point of time. This is one of the feature present under SQL Workshop in Oracle Application Express.
This video shows information on the Oracle Data Dictionary, starting with the Oracle documentation, explaining the different types of Data Dictionary views available by group and permissions as well as giving examples on how to retrieve data from th…
Via a live example, show how to take different types of Oracle backups using RMAN.

728 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

9 Experts available now in Live!

Get 1:1 Help Now