Oracle Concepts: Query on SQL Processing (execution in SGA/PGA)

Hi,
I need some clarity on my understanding, suppose there is a query:
SELECT t1.c1, t1.c2
FROM t1, t2
WHERE t1.c3 = t2.c1
ORDER BY t1.c1;User A submits above query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (unsuccessful) -in SGA
Optimization (Hard Parse) -in SGA
Row Source Generation (Hard Parse) -in SGA
Execution - in SGA?User B submits same query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (successful) -in SGA
(Soft Parse)
Execution - in SGA?First question (General):
I thought Execution happens in SGA, but sorting, hashing, and/or merging bitmaps happens in PGA (temporary segment) so is it a sub-part of Execution that happens in user's PGA?
Second question (For user B):
Once Shared Pool Check is successful, and plan/data-sets are already in SGA, so sorting, hashing, and/or merging bitmaps will happen on these data-sets in user B's PGA again?
Regards,
Ankit Rathi
http://oraclenbeyond.blogspot.in

OnB wrote:
Hi,
I need some clarity on my understanding, suppose there is a query:
SELECT t1.c1, t1.c2
FROM t1, t2
WHERE t1.c3 = t2.c1
ORDER BY t1.c1;User A submits above query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (unsuccessful) -in SGA
Optimization (Hard Parse) -in SGA
Row Source Generation (Hard Parse) -in SGA
Execution - in SGA?User B submits same query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (successful) -in SGA
(Soft Parse)
Execution - in SGA?First question (General):
I thought Execution happens in SGA, but sorting, hashing, and/or merging bitmaps happens in PGA (temporary segment) so is it a sub-part of Execution that happens in user's PGA?The execution happens in the SGA(Buffer cache) but any kinds of such processing like sorting is session specific and that's why it happens in the PGA of that user.
>
Second question (For user B):
Once Shared Pool Check is successful, and plan/data-sets are already in SGA, so sorting, hashing, and/or merging bitmaps will happen on these data-sets in user B's PGA again?Yes.
That said, can you post a link that confirms that the syntax/semantics check happen in the PGA? AFAIK it's not really a part of the PGA because oracle's code itself would store the grammar and would do it .
Aman....

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Hi
Thank for your reply!
I have a nested select query which performs on two different table as shown below:

SELECT LENGTH, WIDTH, HEIGHT, WEIGHT,


LENGTH*WIDTH* HEIGHT AS ITEM_CUBE


FROM CUBE


WHERE ITEM= <abc>


AND OBJECT= (SELECT NAME FROM SUPPLIER WHERE ITEM=<Item> AND SUPP_IND = ‘Y')
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Please suggest how to get it ?

Edited by: user10259700 on Oct 23, 2008 12:17 AM

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Hi all,
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Sankar,
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5     j
102     g
4     g
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c1
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4
3
2
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Hi all,
Hope doing well,
sir i was using one query of sql that is here:
Declare @nshiftmax datetime
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Declare @nshiftmax datetime
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thanks in advance.

952646 wrote:
Hi all,
Hope doing well,
sir i was using one query of sql that is here:
You mean you have these statements in SQL Server?
Please remember that SQL is an access language for relational databases. It is used by all of the major rdbms products. "SQL Server" is the name of Microsoft's rdbms product. Do not let Microsoft's marketing flaks lull you into thinking SQL = SQL Server.
Declare @nshiftmax datetime
set @nshiftmax=convert(time,DATEADD(N,1439,0))
print @nshiftmax
so it is retreiving the result 1/1/1900 11:59 p.m
and one more query is there
Declare @nshiftmax datetime
set @nshiftmax=convert(time,DATEADD(N,0,0))
print @nshiftmax
so it is retreiving the result 1/1/1900 12:00 a.m
how to same result in oracle query.
thanks in advance.

Outer join query for SQL server from Oracle

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SELECT
a."EmpID" as "Employee ID",
a."EmpStatus" "Employee Status"
b."EmpSub" as "Employee Subjects"
FROM
[email protected] a
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http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/queries006.htm#sthref3175
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Like this,
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Edited by: user3614365 on Jun 14, 2012 2:57 PM

please forgive me if my question is too silly.Firs of all, your questions are not silly at all. You can get better understanding of one product by setting analogies and comparisons with a product you are familiar with. I used same method when I learned about MS SQL comparing it with Oracle.
So, welcome on Oracle board!
in MS SQL world, you can install multiple INSTANCE on a physical server, you can have multiple instances of Oracle, belonging to same or separate Oracle Home on same physical machine.
inside each INSTANCE, you can create multiple DATABASEs, In Oracle instance you can have only one database. That is how it is.
each DATABASE has it owned data\transaction log file on disk.Even in MS SQL there can be multiple data files per database.
>
In the Oracle world, my understand is, INSTANCE = memory structure + physical database file (which pretty close to MS SQL identification). similar to MS SQL, you can have multiple INSTANCEs on each physical server.
>
yes
>
but which one is the 'DATABASE' in oracle world? The closest one i think is TABLESPACE. I can assign one or multiple physical data file for each TABLESPACE. but all the TABLESPACE place the redo log file inside the same undo TABLESPACE?
>
Here is little similarity between Oracle TABLESPACE and MS SQL database.
In MS SQL Database has not only files associated with it, it has its own security and piece of data dictionary. It can have its own collation, you can detach it from one instance and attach to another, you can back it up separately, etc...
I would say MS DB is more "standalone and self-containig" unit, comparing to Oracle TS.
Oracle TS is a way of organizing data files and setting some default common storage properties for tables and other segments contained in TS.
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Anyway Oracle TS is not even close thing to MS DB.
And it does not need to be. It has a totally different purpose.
also, for each application, i have to create one or more TABLESPACE inside a INSTANCE(that's what i usually do in MS SQL)?You do not have to. But you better to do this way, from a data organization perspective. To make things look nicely organized.
Sometimes one application may use multiple TS, for example when it needs different block size for some tables.
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I have searched but could not find any specific document.
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Hi;
Please see:
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http://docs.oracle.com/cd/E18727_01/doc.121/e13652/T321962T321965.htm
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For r11:
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How to write exact query from sql to oracle?

Hi all,
hope doing well,
sir i am using one query in sql that is
declare @earlyleavers varchar(max), @earlyleavers1 int
select @earlyleavers1 = DATEDIFF(Minute,'1900/01/01 10:00:00.000','1900/01/01 11:00:00.000')
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please help me.
thanks in advance.

952646 wrote:
sir i need result in this format 01:00 not in 1 format.The name is Billy and not "sir". :-)
Is "01:00" a string format or an elapsed time format?
The number that the above code returns is decimal hours. So a number value of 1.5 means 1h30m or 1:30 or however you need to render that.
And that is the question. Is this a rendering issue? Must the result be rendered in a specific format?
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2          earlyleavers    interval day to second;
3 begin
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6                                  to_date('1900/01/01 10:00:00','yyyy/mm/dd hh24:mi:ss') ) * 24,
7                                  'hour'
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9
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PL/SQL procedure successfully completed.
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SQL Query ( PL/SQL function body returning query ) page

Hello Friends,
I have a page with type SQL Query ( PL/SQL function body returning query ).
I have written a pl/sql block that returns a sql query - select statment.
Some times i am getting no data found error - does it got to do with the variable that stores the query .
=======================
ORA-06502: PL/SQL: numeric or value error: character string buffer too small
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====================
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l_where varchar2(32000);
l_order_by varchar2(32000);
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=============================
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It looks like the query string you are trying to pass back exceeds the 32K limit for a varchar. Where this is happening is kind of difficult to tell as it could be any number of points, and also depends on what you are passing into the process via page items.
I would first try to establish what combination of page items causes this error to occur. Then, starting from the bottom and working your way backwards, I would start 'switching off' some of the items you use to build your query until it breaks again, thus establishing which part is leading to the error.
Also, I'm not sure what :P10_STMT is doing (are you maybe using this for visiblity of the query created)?
It looks like the query string you are trying to pass back exceeds the 32K limit for a varchar. Where this is happening is kind of difficult to tell as it could be any number of points, and also depends on what you are passing into the process via page items.
I would first try to establish what combination of page items causes this error to occur. then, starting from the bottom and working your way backwards, I would start 'switching off' some of the items you use to build your query until it breaks again, thus establishing which part is leading to the error.
Also, I'm not sure what :P10_STMT is doing (are you maybe using this for visiblity of the query created)?

DB buffer cache vs. SQL query & PL/SQL function result cache

Hi all,
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There is also additional otion - SQL query & PL/SQL function result cache (from 11g), where also stored the results of such queries.
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thanks in advance...

There is also additional otion - SQL query & PL/SQL function result cache (from 11g), where also stored the results of such queries.Result cache located in shared pool.So it is one component of shared pool.When server process execute query(and if you configured result cache) then result will store in shared pool.Then next execution time run time mechanism will detect and consider using result cache without executing this query(if data was not changed this is happen detection time)
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Edited by: Chinar on Nov 4, 2011 4:40 AM
(Removing lots of "But" word from sentences :-) )

Oracle Concepts: Query on SQL Processing (execution in SGA/PGA)

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