Solved

Optimization of nested queries

Posted on 2008-10-23
5
418 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
ID: 22784988

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
ID: 22784994
This techinique is called "Subquery factoring".
0
 

Author Comment

by:gursheenz2008
ID: 22785432
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
ID: 22785445
is noinp a unique key for synoup?
0
 
LVL 14

Accepted Solution

by:
GGuzdziol earned 250 total points
ID: 22785535
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.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

How to Unravel a Tricky Query Introduction If you browse through the Oracle zones or any of the other database-related zones you'll come across some complicated solutions and sometimes you'll just have to wonder how anyone came up with them.  …
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, step by step, how to configure Oracle Heterogeneous Services via the Generic Gateway Agent in order to make a connection from an Oracle session and access a remote SQL Server database table.
This videos aims to give the viewer a basic demonstration of how a user can query current session information by using the SYS_CONTEXT function

776 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