Is selecting from a view more efficient than selecting from multiple tables

Hi heres the problem
Lets say i created a view from 2 tables (person and info). both have a ID column
create view table_view (age,name,status,id) as
select a.age, a.name, b.status, b.id
from person a, info.b
where a.id=b.idif i want to select a given range of values from these 2 tables which of the following queries would be more effective.
select a.age, a.name, b.status, b.id
from person a, info.b
where a.id=b.id
and a.id <1000
select age, name, status, id
from table_view
where id <1000

Bear in mind that this concept of views storing the SQL text is something relative to Oracle databases and not necessarily other RDBMS products. For example, Ingres databases create "views" as tables of data on the database and therefore there is a difference between selecting from the view and selecting from the base tables.
Oracle also has "materialized views" which differ from normal "views" because they are actually created, effectively, as tables of data and will not use the indexes of the base tables.
In Oracle, you cannot create indexes against "views" but you can create indexes against "materialized views".

Similar Messages

Sender JDBC adapter SELECT / UPDATE issue - updates more rows than selected

Hi,
We have configured a Sender JDBC Adapter to poll records from an Oracle table based on a flag field and then update the flag for the selected records. When tested in DEV and QA environments (where test data comes in intermittently and not in huge volumes), itu2019s working fine.
Both SELECT and UPDATE queries written in the Sender JDBC adapter are getting properly executed and are changing the status of the flag for the selected records from Y to N once read from the database.
select * from <table> where flag = 'N'.
update <table> set flag = 'Y' where flag = 'N'.
But in the PROD environment (with records getting updated in the database every second), after XI executes the SELECT query and just before the UPDATE query is executed, new records come into the Oracle table with status flag 'N". So when the UPDATE query runs just after the SELECT query, then these unselected records also get updated to 'Y'. Thus these records never get into the resultset and hence XI and thus remain unprocessed.
So when XI does a SELECT and UPDATE on the Oracle DB table and concurrently there is an INSERT happening into the table from the other end, the JDBC sender adapter is picking up a certain number of records but updating the status of more records than it picked up.
So how does XI deal with such a common scenario without dropping records?
Thanks,
Vishak

The condition being checked is the same for both SELECT and UPDATE statements.
Initially I tried setting transaction isolation levels on the database to repeatable_read and serializable but it was throwing me a java.sql.SQLException error saying that these transaction levels were not valid.
I asked for these transaction level permissions for the XI user from my DBA but the DB I am accessing provides only a view into other databases and so it's not possible.

Why is Array more efficient than flexible-size collection

it is a bit more tricky to understand the two advantges of Array as following:
1. access to items held in an array is often more efficient than access to the items in a comparable flexible-size collection,
2. arrays are able to store objects or primitive -type values, but flexible -size collection can store only object.
thanks in advance

it is a bit more tricky to understand the two
wo advantges of Array as following:
1. access to items held in an array is often more
e efficient than access to the items in a comparable
flexible-size collection,The standard dynamic data structure (with standard I mean member of the collections framework) comparable to the array is the ArrayList. In principle the access to an element is equally efficient in both cases. (There's some overhead because you have to do a method call in the ArrayList case). It's only in very low-level algoritms you need to use arrays. In most cases ArrayList is fine.
2. arrays are able to store objects or primitive
ve -type values, but flexible -size collection can
store only object.This is true with the standard collection, but there are alternative collections that can store primitives, for example,
http://pcj.sourceforge.net/
In the next version of Java there's a new concept call autoboxing. This means there's an implicit conversion taking place between primitive types and their corresponding wrapper class, say between int and Integer. This means you will be able to write your program AS IF you could store primitives in the standard collections.

HT5129 everything has been moved. how do you stop it from asking any more and remove MobileMe from preferences?

everything has been moved. how do you stop it from asking any more and remove MobileMe from preferences?

Ferd II solved it.
Go to iPhoto>Preferences...>Accounts...and remove the MobileMe account. Then go to System Preferences...>MobileMe, and sign out.

Is a WITH...SELECT query more efficient than a SELECT query ?

Hi folks,
Is the WITH...SELECT just a convenience or is it really efficient than a simple SELECT with UNION ALL ? e.g. is the following:
with rset as (select dname,empno,ename,hiredate,sal from emp e,dept d where e.deptno=d.deptno)
select dname,empno,ename,hiredate,sal,
case
when trunc(hiredate) < to_date('19800101','yyyymmdd') then 'Hired before 1980'
when trunc(hiredate) between to_date('19800101','yyyymmdd') and to_date('19851231','yyyymmdd') then 'Hired between 1980 and 1985'
else 'Hired after 1985'
end as notes
from rset
union all
select dname,empno,ename,hiredate,sal,
case
when sal < 500 then 'Salary less than 500'
when sal between 501 and 1500 then 'Salary between 501 and 1500'
else 'Salary greater than 1500'
end as notes
from rset;
better than the following:
select dname,empno,ename,hiredate,sal,
case
when trunc(hiredate) < to_date('19800101','yyyymmdd') then 'Hired before 1980'
when trunc(hiredate) between to_date('19800101','yyyymmdd') and to_date('19851231','yyyymmdd') then 'Hired between 1980 and 1985'
else 'Hired after 1985'
end as notes
from emp e,dept d where e.deptno=d.deptno
union all
select dname,empno,ename,hiredate,sal,
case
when sal < 500 then 'Salary less than 500'
when sal between 501 and 1500 then 'Salary between 501 and 1500'
else 'Salary greater than 1500'
end as notes
from emp e,dept d where e.deptno=d.deptno;
I am a newbie at sql tuning. Apparently, the first query should be faster because it runs the actual query only once and then just works on the resultset obtained. Is this thinking correct ?
Thanks a lot!!
JP

Also I tried a test here with a ten million row emp table queried five times, and explain plan showed the optimizer would read emp five times and not once.
Re: Intresting question
Apparently, the first query should be faster because it runs the actual query only once
and then just works on the resultset obtained.But my test combined with Jonathan's article made me question whether materializing ten million rows somewhere would be faster than querying them five times. Somehow I doubt it.

Would PHP or Python work more efficiently to grab from a MSSQL database in AS3?

Would PHP or Python work more efficiently to grab information from a MSSQL database in AS3? How would it work? Thanks!

that's not a flash issue.
but here's a comparison, http://benchmarksgame.alioth.debian.org/u32/benchmark.php?test=all&lang=python&lang2=php
which looks like python would be faster at data handling and slow at arithmetic operations.
you would call both server-side scripts using the urlloader class from flash.

Help needed from someone far more clever than me.

I'm trying to update the software on my e71 using Nokia software updater.
Everything seemed to be running smoothly. My software was being updated from 100.something to 110.something.
Then, as it was finishing my computer screen kept flashing up the message...
"A new USB device has been detected...
Nokia USB ROM
And then it asks me whether I want to connect the device to my Mac or the Virtual machine (I'm doing this via parallels on my mac).
This message flashes on and off intermittently, and it doesn't matter whether you click the 'virtual machine button'.
The download bar sticks and the information given is that it will downoad in 15 mins.
I have tried rebooting the computer, the phone. Nothing is working. It's very frustrating. Most frustrating of all, as the programme is still running it won't let me quit so I have to force quit the whole machine.
Any help gratefully received.
Thankyou.

03-Dec-2008 10:42 AM
benjamin163 wrote:
Hey Rabi, we're you suggesting that the phone should be in offline mode whilst doing an upgrade? Why is that?
If he did, he's incorrect. Instructions say specifically that the phone must be in "General" profile.
As for N96 firmware updates, they're more often than not going to be by FOTA, which removes the need for a computer altogether. When I updated from 10.065 to 11.018, I did so by FOTA, but 11.018 to 11.101 was using NSU (and it failed first time round, too). Had I waited, I could have done that update by FOTA as well.
Was this post helpful? If so, please click on the white "Kudos!" star below. Thank you!

Viewing more values on Graph from DAQ Card

Hello,
I am acquiring a Signal using DAQ Card, the problem is that i can view only few values on the Waveform Graph. Kindly guide me if i want to view more points on the waveform graph, what should i do in my programming window.
Regards

Hi Abuzar,
your VI is just an expressVI and a graph - nearly to nothing…
- Why do you set the DAQAssistent to "limited number of samples", when you want to have a continuous measurement?
- Did you look at the example VIs coming with LabVIEW? Those that explain DAQmx functions?
- A graph only displays the data in the wire you feed to. When you want to display more data you need to collect it. When you really want to stick with expressVIs then you could use the one, which allows appending signals…
- Learn to use shift registers!

Under what circumstances are recursion more efficient than loops

Although recursion do provide a cleaner code and often suggests a more interesting approach to a problem, it nonetheless is relatively more resource consuming for solving some of the more novice programming feats (such as facorial calculation or binary conversion). Can somebody give me an example of a more practical and efficient use of recursion?

Can somebody give me an example
of a more practical and efficient use of recursion?What do you mean by practical or efficient? Most tree traversal implementations are recursive since it's much easier to traverse trees using recursion.
Kaj

Is there something more efficient than EXISTS statement?

Hi All,
I have this query:
select
waco,
ltrim(rtrim(wammcu)) as wammcu,
wadoco,
walitm,
wadl01,
case
when wastrx = 0
then null
else
proddta.JulianToDate(wastrx)
end
AS wastrx,
wauom,
cast(wasoqs / 10000 as numeric (15,4)) as wasoqs,
cast(wasocn / 10000 as numeric (15,4)) as wasocn,
--THIS IS THE PART TO OPTIMIZIE
(select
sum(cast(glaa / 100 as numeric (15,2)))
from
proddta.f0911
where
glkco=waco and
glco =waco and
gldct='IV' and
glsblt = 'W' and
glsbl = right(replicate('0',8) + CONVERT(varchar,CONVERT(int,wadoco)),8) and
exists
(select * from proddta.f4095
where
mlanum in (3220,3260,3270,3280) and
mlco=glco and
mldcto=wadcto and
mldct=gldct and
mlcost='A1' and
mlobj=globj)) as A1_Account
--END OF THE PART TO OPTIMIZE
from
proddta.f4801
where
waco='00010' and
wadcto='WO' and
wasrst='99' and
wastrx >= 114001
and exists
select
from
proddta.f0911
where
glkco=waco and
glco =waco and
gldct='IV' and
glsblt = 'W' and
glsbl = right(replicate('0',8) + CONVERT(varchar,CONVERT(int,wadoco)),8) and
gldgj between 114001 and 114031
It takes a very long time to execute, my T-SQL is almost rusted, is there a way to improve the query with new costruct T-SQL has?

This is the query plan:
StmtText
|--Compute Scalar(DEFINE:([Expr1008]=CASE WHEN [JDE_PROD].[PRODDTA].[F4801].[WASTRX]=(0.) THEN NULL ELSE [JDE_PROD].[PRODDTA].[JulianToDate](CONVERT_IMPLICIT(int,[JDE_PROD].[PRODDTA].[F4801].[WASTRX],0)) END, [Expr1020]=[Expr1018]))
|--Nested Loops(Inner Join, OUTER REFERENCES:([JDE_PROD].[PRODDTA].[F4801].[WADCTO], [JDE_PROD].[PRODDTA].[F4801].[WADOCO], [JDE_PROD].[PRODDTA].[F4801].[WACO]))
|--Hash Match(Right Semi Join, HASH:([JDE_PROD].[PRODDTA].[F0911].[GLSBL])=([Expr1021]), RESIDUAL:([JDE_PROD].[PRODDTA].[F0911].[GLSBL]=[Expr1021]))
| |--Clustered Index Seek(OBJECT:([JDE_PROD].[PRODDTA].[F0911].[F0911_PK]), SEEK:([JDE_PROD].[PRODDTA].[F0911].[GLDCT]=N'IV'), WHERE:([JDE_PROD].[PRODDTA].[F0911].[GLDGJ]>=(114001.) AND [JDE_PROD].[PRODDTA].[F0911].[GLDGJ]<=(114031.)
AND [JDE_PROD].[PRODDTA].[F0911].[GLKCO]=N'00010' AND [JDE_PROD].[PRODDTA].[F0911].[GLCO]=N'00010' AND [JDE_PROD].[PRODDTA].[F0911].[GLSBLT]=N'W') ORDERED FORWARD)
| |--Compute Scalar(DEFINE:([Expr1007]=ltrim(rtrim([JDE_PROD].[PRODDTA].[F4801].[WAMMCU])), [Expr1009]=CONVERT(numeric(15,4),[JDE_PROD].[PRODDTA].[F4801].[WASOQS]/(1.000000000000000e+004),0), [Expr1010]=CONVERT(numeric(15,4),[JDE_PROD].[PRODDTA].[F4801].[WASOCN]/(1.000000000000000e+004),0),
[Expr1021]=CONVERT_IMPLICIT(nvarchar(8),right('00000000'+CONVERT(varchar(30),CONVERT(int,[JDE_PROD].[PRODDTA].[F4801].[WADOCO],0),0),(8)),0)))
| |--Clustered Index Scan(OBJECT:([JDE_PROD].[PRODDTA].[F4801].[F4801_PK]), WHERE:([JDE_PROD].[PRODDTA].[F4801].[WASTRX]>=(114001.) AND [JDE_PROD].[PRODDTA].[F4801].[WACO]=N'00010' AND
[JDE_PROD].[PRODDTA].[F4801].[WADCTO]=N'WO' AND [JDE_PROD].[PRODDTA].[F4801].[WASRST]=N'99'))
|--Compute Scalar(DEFINE:([Expr1018]=CASE WHEN [Expr1031]=(0) THEN NULL ELSE [Expr1032] END))
|--Stream Aggregate(DEFINE:([Expr1031]=COUNT_BIG([Expr1022]), [Expr1032]=SUM([Expr1022])))
|--Hash Match(Right Semi Join, HASH:([JDE_PROD].[PRODDTA].[F4095].[MLOBJ])=([JDE_PROD].[PRODDTA].[F0911].[GLOBJ]), RESIDUAL:([JDE_PROD].[PRODDTA].[F4095].[MLOBJ]=[JDE_PROD].[PRODDTA].[F0911].[GLOBJ]))
|--Clustered Index Seek(OBJECT:([JDE_PROD].[PRODDTA].[F4095].[F4095_PK]), SEEK:([JDE_PROD].[PRODDTA].[F4095].[MLANUM]=(3.220000000000000e+003) AND [JDE_PROD].[PRODDTA].[F4095].[MLCO]=[JDE_PROD].[PRODDTA].[F4801].[WACO]
AND [JDE_PROD].[PRODDTA].[F4095].[MLDCTO]=[JDE_PROD].[PRODDTA].[F4801].[WADCTO] AND [JDE_PROD].[PRODDTA].[F4095].[MLDCT]=N'IV' OR [JDE_PROD].[PRODDTA].[F4095].[MLANUM]=(3.260000000000000e+003) AND [JDE_PROD].[PRODDTA].[F4095].[MLCO]=[JDE_PROD].[PRODDTA].[F4801].[WACO]
AND [JDE_PROD].[PRODDTA].[F4095].[MLDCTO]=[JDE_PROD].[PRODDTA].[F4801].[WADCTO] AND [JDE_PROD].[PRODDTA].[F4095].[MLDCT]=N'IV' OR [JDE_PROD].[PRODDTA].[F4095].[MLANUM]=(3.270000000000000e+003) AND [JDE_PROD].[PRODDTA].[F4095].[MLCO]=[JDE_PROD].[PRODDTA].[F4801].[WACO]
AND [JDE_PROD].[PRODDTA].[F4095].[MLDCTO]=[JDE_PROD].[PRODDTA].[F4801].[WADCTO] AND [JDE_PROD].[PRODDTA].[F4095].[MLDCT]=N'IV' OR [JDE_PROD].[PRODDTA].[F4095].[MLANUM]=(3.280000000000000e+003) AND [JDE_PROD].[PRODDTA].[F4095].[MLCO]=[JDE_PROD].[PRODDTA].[F4801].[WACO]
AND [JDE_PROD].[PRODDTA].[F4095].[MLDCTO]=[JDE_PROD].[PRODDTA].[F4801].[WADCTO] AND [JDE_PROD].[PRODDTA].[F4095].[MLDCT]=N'IV'), WHERE:([JDE_PROD].[PRODDTA].[F4095].[MLCOST]=N'A1') ORDERED FORWARD)
|--Index Spool(SEEK:([JDE_PROD].[PRODDTA].[F0911].[GLKCO]=[JDE_PROD].[PRODDTA].[F4801].[WACO] AND [JDE_PROD].[PRODDTA].[F0911].[GLCO]=[JDE_PROD].[PRODDTA].[F4801].[WACO]
AND [JDE_PROD].[PRODDTA].[F0911].[GLSBL]=CONVERT_IMPLICIT(nvarchar(8),right('00000000'+CONVERT(varchar(30),CONVERT(int,[JDE_PROD].[PRODDTA].[F4801].[WADOCO],0),0),(8)),0) AND [JDE_PROD].[PRODDTA].[F0911].[GLDCT]=N'IV' AND [JDE_PROD].[PRODDTA].[F0911].[GLSBLT]=N'W'))
|--Compute Scalar(DEFINE:([Expr1022]=CONVERT(numeric(15,2),[JDE_PROD].[PRODDTA].[F0911].[GLAA]/(1.000000000000000e+002),0)))
|--Clustered Index Scan(OBJECT:([JDE_PROD].[PRODDTA].[F0911].[F0911_PK]))
it returns 1734 rows, the tables queried contain milions of roiw

Is FLV more efficient than m2ts as a proxy?

FLV is considerable smaller than m2ts but I wonder if it is less taxing on the system.

The strategy that is better is writing the code in the clearest way possible. If you're creating 10 new objects, call new 10 times.

Hp color LaserJet 5550 print more copies than requested in multiple copies print

Hi, I've got a hp color LaserJet 5550 on a network, when I send to print more than one copy (2 for instance) I get more than 2 copies, last time I got 4.
Any suggestion? I've seen on other forums that I must disable bidirectional connection, it's done, drivers are new.
Thank you.

Good day,
To get your issue more exposure, I would suggest posting it in the commercial forums since your product is a commercial product. You can do this at Commercial Forums.
Enjoy your day!
R a i n b o w 7000I work on behalf of HP
Click the “Kudos Thumbs Up" at the bottom of this post to say
“Thanks” for helping!
Click “Accept as Solution” if you feel my post solved your issue, it will help others find the solution!

Materialized view to ensure data integrity over multiple tables

Hello,
I have a problem and I am not able to solve it. Partially, It is because of my poor SQL skills. I have three tables and I am using one sequence to enter data into them.
What I am tying to do is to create a materialized view ( complete or fast, whichever) with refresh on commit option to check that each table contains unique data in comparison to other.
I am posting code so you can get along:
CREATE TABLE table_1 (
ID NUMBER PRIMARY KEY
CREATE TABLE table_2 (
ID NUMBER PRIMARY KEY
CREATE TABLE table_3 (
ID NUMBER PRIMARY KEY
INSERT INTO table_1 VALUES (1);
INSERT INTO table_1 VALUES (2);
INSERT INTO table_2 VALUES (3);
INSERT INTO table_2 VALUES (4);
INSERT INTO table_3 VALUES (5);
INSERT INTO table_3 VALUES (6); I want to write create a materialized view that will give me output only in case that there are same values in two different tables. I got this far.
CREATE MATERIALIZED view mv_test
REFRESH COMPLETE ON COMMIT
AS
SELECT count(1) ROW_COUNT
FROM dual
WHERE EXISTS (
     SELECT a.id
     FROM table_1 a
     WHERE a.id IN(
         SELECT b.id
         FROM table_2 b))
OR EXISTS (
    SELECT a.id
     FROM table_1 a
     WHERE a.id IN
             (SELECT c.id
             FROM table_3 c))
OR EXISTS (
    SELECT b.id
         FROM table_2 b
    WHERE b.id IN
             (SELECT c.id
             FROM table_3 c));
    ALTER MATERIALIZED VIEW mv_test
    ADD CONSTRAINT cs_mv_test
    CHECK (row_count = 0) DEFERRABLE; This sql statement itself returns no rows if my logic is correct. And in case there were some duplicate rows in two different table, it would return 1 and constraint would throw an error.
However, I cannot create this with ON COMMIT option. When I try to compile I get:
ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view I went through documentation, tried creating mat_view logs etc.
I know that one of the mistakes is that I am referencing dual table and I am not sure if I can use EXISTS.
Unfortunately, my SQL wisdom ends here. I need help rewriting the sql, so it would work in materialized view with refresh on commit option. Please, help!!!
I know that since I am using a sequence there is little chance that same value will get into two different tables, but I would like to perform somekind of check.
Thank you in advance.

>
I know that since I am using a sequence there is little chance that same value will get into two different tables, but I would like to perform somekind of check.If you are certain that you control all the inputs to the table and you are definitely using one sequence to insert into all three tables then there is physically no possible way you will get duplicate values across tables.
Writing something to check if this is the case would almost be like writing something to verify that 1+1 really does equal 2 in 100% of cases.
if you must, however. consider something similar to the following which may be more performant:
select *
from table_1 t1
full outer join table_2 t2 on (t1.id = t2.id)
full outer join table_3 t3 on (t1.id = t2.id
                                 or
                                 t2.id = t3.id)
where t1.id+t2.id+t3.id not in (t1.id,t2.id,t3.id);

Firing a view based on a selection from a popup window

Hi,
I have a main window in which there is "Display Details" button and a view container to hold a view. On clicking this display button I'm showing a pop-up window which will show the user the options to select a particular view. After the selection and clicking on OK in the pop up window the corresponding view should be shown the view container.
I tried this by firing an outboung plug to the corresponding view based on the selection in the popup window. The problem is I cannot create a navigation link in the window as the popup view is not part of the main window.
Could you please provide me your insights on how to handle this scenario?
Regards,
Vivek

Hi Vivek,
Please refer this article: [Creating Navigations and Embedding Views at Runtime - Web Dynpro ABAP|http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/50f3660d-ad29-2b10-2482-8120e56942dd?QuickLink=index&overridelayout=true]. Also refer [Thomas' reply in this thread|Embed a view dynamically in a ViewContainerUIElement;.
Regards

3 Table Joins -- Need a more efficient Query

I need a 3 table join but need to do it more efficiently than I am currently doing. The query is taking too long to execute (in excess of 20 mins. These are huge tables with 10 mil + records). Here is what the query looks like right now. I need 100 distinct acctnum from the below query with all the conditions as requirements.
THANKS IN ADVANCE FOR HELP!!!
SELECT /*+ parallel */
FROM (SELECT /*+ parallel */ DISTINCT (a.acctnum),
                              a.acctnum_status,
                              a.sys_creation_date,
                              a.sys_update_date,
                              c.comp_id,
                              c.comp_lbl_type,
                              a.account_sub_type
              FROM   account a
                     LEFT JOIN
                        company c
                     ON a.comp_id = c.comp_id AND c.comp_lbl_type = 'IND',
                     subaccount s
             WHERE       a.account_type = 'I'
                     AND a.account_status IN ('O', 'S')
                    and s.subaccount_status in ('A','S')
                     AND a.account_sub_type NOT IN ('G', 'V')
                     AND a.SYS_update_DATE <= SYSDATE - 4 / 24)
where   ROWNUM <= 100 ;

Hi,
Whenever you have a question, post CREATE TABLE and INSERT statements for a little sample data, and the results you want from that data. Explain how you get those results from that data.
Simplify the problem, if possible. If you need 100 distinct rows, post a problem where you only need, say, 3 distinct rows. Just explain that you really need 100, and you'll get a solution that works for either 3 or 100.
Always say which version of Oracle you're using (e.g. 11.2.0.3.0).
See the forum FAQ: https://forums.oracle.com/message/9362002
For tuning problems, also see https://forums.oracle.com/message/9362003
Are you sure the query you posted is even doing what you want? You're cross-joining s to the other tables, producing all possible combinations of rows, and then picking 100 of those in no particular order (not even random order). That's not necessarily wrong, but it certainly is suspicious.
If you're only interested in 100 rows, there's probably some way to write the query so that it picks 100 rows from the big tables first.

Is selecting from a view more efficient than selecting from multiple tables

Similar Messages

Maybe you are looking for