CBO and FROM clause

hi,
is the concept of ordering of tables in FROM clause still valid for CBO.
I mean the concept of oracle selecting the driving table based on the positions of table in FROM clause still valid??
If yes, then how should the tables be placed? the one with least rows in the end of from clause??
Also is it better to leave to CBO or put a /*+ORDER */ hint??because additional time will be wasted by CBO in collecting stats??
Any authentic document which speaks about optimization techniques??( i mean SQL tuning rules)
s
Message was edited by:
user571638

When I started, my focus was also on SQL tuning rules but I found out that this was not the most efficient way to tune performance. You can save a lot of time on performance tuning when you let the CBO work for you:
http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14211/toc.htm

Similar Messages

Record Group and From-Clause Datasource

I need to do several complex queries (read-only) for my form. Original I used From-Clause datasource but, as the requirement changed, there are some limitations. I would rather no do anything dynamically if as all possible because there are over 20 such queries which makes the code difficult to maintain. I wanted to be able to reference block items in the query.
I'm thinking about using Record Group query instead. What are the differences in capability between Record Groups and From-Clause Datasource?
Thanks.
Clayton.

Thanks.
That's exactly the problem I have. I don't want to use LOVs so I've been thinking about how to visualize the record group data using data blocks. Perhaps I'll just go with dynamically building the From-Clause.
I've looked into stored procedure based blocks a bit; it was confusing for me. Are the stored procedures stored in the database or are they defined in the form?

Update statement that includes case, decode and from clause

hello
I've the following code. I ran this code in 9i and got the errror SQL command not properly ended. Can I use FROM clause in an update statement?
CREATE OR REPLACE procedure NRI
IS
BEGIN
UPDATE IEB2 SET SDI =
(CASE PSDI WHEN '11' THEN '16'
WHEN '13' THEN '38'
WHEN '14' THEN '18'
WHEN '23' THEN '21'
WHEN '24' THEN '21'
WHEN '31' THEN '27'
WHEN '32' THEN '37'
WHEN '33' THEN '38'
WHEN '34' THEN '37'
WHEN '43' THEN '46'
WHEN '53' THEN '45'
WHEN '55' THEN '48'
WHEN '60' THEN '54'
WHEN '61' THEN '57'
WHEN '62' THEN '54'
WHEN '63' THEN '56'
WHEN '64' THEN '52'
WHEN '70' THEN '21'
WHEN '77' THEN '25'
WHEN '78' THEN '41'
WHEN '80' THEN '79'
WHEN '85' THEN '75'
WHEN '87' THEN '73'
WHEN '15' THEN '15'
WHEN '51' THEN '51'
WHEN '88' THEN '88'
WHEN '00' THEN '00'
WHEN '99' THEN '99'
WHEN '12' THEN DECODE(C.R_ID, 'N', '16','18')
ELSE 'NONE' END)
FROM D1.C C
WHERE EXISTS
(SELECT 1
FROM D1.SD A, D2.SDP B, D1.C C
WHERE A.SDN = B.DN
AND B.SDI = '000000'
AND B.PFI = 'W'
AND B.CID = C.CID
AND A.SDN = '0001500721');
END;

Your parenthesis look a tad messed up ... think this fixes them.
CREATE OR REPLACE procedure NRI
IS
BEGIN
UPDATE IEB2 SET SDI =
SELECT
CASE PSDI
WHEN '11' THEN '16'
WHEN '13' THEN '38'
WHEN '14' THEN '18'
WHEN '23' THEN '21'
WHEN '24' THEN '21'
WHEN '31' THEN '27'
WHEN '32' THEN '37'
WHEN '33' THEN '38'
WHEN '34' THEN '37'
WHEN '43' THEN '46'
WHEN '53' THEN '45'
WHEN '55' THEN '48'
WHEN '60' THEN '54'
WHEN '61' THEN '57'
WHEN '62' THEN '54'
WHEN '63' THEN '56'
WHEN '64' THEN '52'
WHEN '70' THEN '21'
WHEN '77' THEN '25'
WHEN '78' THEN '41'
WHEN '80' THEN '79'
WHEN '85' THEN '75'
WHEN '87' THEN '73'
WHEN '15' THEN '15'
WHEN '51' THEN '51'
WHEN '88' THEN '88'
WHEN '00' THEN '00'
WHEN '99' THEN '99'
WHEN '12' THEN DECODE(C.R_ID, 'N', '16','18')
ELSE 'NONE'
END
FROM D1.C C
WHERE EXISTS
    SELECT 1
    FROM D1.SD A, D2.SDP B, D1.C C
    WHERE A.SDN = B.DN
    AND B.SDI = '000000'
    AND B.PFI = 'W'
    AND B.CID = C.CID
    AND A.SDN = '0001500721'
END;

KEY-EXEQRY trigger and FROM CLAUSE QUERY problem

Hi,
I have a form designed in Oracle Forms6i. I have two block on it, BlockA and BlockB.
When BlockA is queried with some data to search, I need to build the FROM CLAUSE QUERY for BlockB. It uses the same WHERE condition as I used to search BlockA.
I am building the FROM CLAUSE QUERY and executing query for BlockB on KEY-EXEQRY trigger of BlockA.
It works fine, if first time, I query the BlockA without any specific data. But it gives me error 'ORA-01008: not all variables bound' if I query the BlockA with specific data very first time.
Please advise.
Thanx
Zaaf

No, I am not using any substitution variables. To get the LAST_QUERY for BlockA, I am using Get_Block_Property.
But now I switched it to :system.LAST_QUERY and it worked.
Thank you!

SQL Select and From Functions

Can sql aggregate functions be added to an interface select clause and from clause.
I want to have a datasource where one of the columns is an aggregate such as a count, which would need the ability to indicate a from clause function group by, or having by. In the Designer Diagram tab for the interface, it seems you can only apply sql functions to where clause joins or filters.
I want to have a query such as follows as my datasource
select columnA, count(*) as thecount
from table x
group by columnA
order by thecount asc
and ultimately
select columnA, thecount
from (select columnA, count(*) as thecount
from table x
group by columnA
order by thecount asc)
where rownum <1001
Can this be done in the ODI Designer, without creating a physical custom view on the database?

Hi lpantuso,
Aggregate functions are added by ODI automatically. In this case you would want mappings like this:
TARGET_COL_1: columnA
TARGET_COL_2: count(*)
ODI will generate something like this:
select
 columnA,
 count(*)
from MY_TABLE MY_TABLE
where
 (1=1)
Group By MY_TABLE.columnA
The subselect, however, isn't handled out of the box. In general ODI isn't quite as friendly with ordering clauses since order by is not relational. (Sets aren't ordered.) To get only the first 1000 columnA values, you'll probably need to create a view or break it into 2 separate interfaces.
Regards,
Matt

Sequence of tables in from clause and sequence of "where clause" conditions

Is Sequence of tables in "From Clause" and sequence of "where clause" conditions matters in 10g for performance?
Edited by: user6763079 on Jun 1, 2011 3:33 AM

user6763079 wrote:
Is Sequence of tables in "From Clause" and sequence of "where clause" conditions matters in 10g for performance?In general it does not matter.
It could matter if the Rule Based Optimizer (RBO) is used. However this RBO is only used if enforced by a hint or if no table statistics are collected. Starting from 10g the table statistics are automatically selected by a regular database job. So in general the CBO would be used.
The CBO will consider different access paths. If the number of tables is low enough, then all possible combinations are considered and the order does not make any difference.
Edited by: Sven W. on Jun 1, 2011 4:00 PM

FROM Clause Query and Invisible records :(

HI:
My form has a block based on a FROM clause query (QUERY DATA SOURCE TYPE).
This works fine with no errors. Count hits suggests that it is retrieving records but my Item is not displaying the records. I have nine records in total but all fields are blank even though I can 'scroll' through the nine (invisible) records.
Strange, any ideas people ?
thanks.
N.

Thanks you for the reply but its not the cause of the 'probem'. My items are in a multi record block ( I have tried single item bock / No Items displayed 1 etc..) but to no avail.
The strange thing about it is that I can Message(:blk.item) and the value displays on the Message bar but there are no values displayed in the Canvas Item at runtime ????? Very strange or does someone know something I dont.
I can even scroll to the end of the record set ( 9 recs).
I have never caome across this before has anyone else ?
Thanks
N.

Block based on "From clause query" and substitution variable

Hi Folks,
I have a "From clause query" block type, which is based on query that uses a substitution variable (:BLOCK.COLUMN) from previous block. When I run a query, then I obtain an error: ORA-01008: not all variables bound.
My query looks like:
select seq_no, prod_code, descr, curr_code,
 max(decode(sched_type_code,'ROLLOVER',amt,0)) OUTSTD_DRAW,
 max(decode(sched_type_code,'INTCHG',amt,decode(sched_type_code,'FEEREC',amt,0))) OUTSTD_INTEREST_FEE
from
 select r.fac_no, r.prod_code, f.descr, r.prod_seq_no seq_no, r.curr_code, r.sched_type_code,sum(nvl(rep_amt,0)) amt
 from repay_scheds r,
 fac_prods f
 where r.fac_no = f.fac_no
 and r.prod_code = f.prd_code
 and r.prod_seq_no = f.seq_no
 and r.fac_no = :B2.FAC_NO
 and r.trans_ref_from is not null
 and r.status <> 'P'
 group by r.fac_no, r.prod_code, f.descr, r.prod_seq_no, r.curr_code, r.sched_type_code
group by seq_no, prod_code, descr, curr_code
having max(decode(sched_type_code,'ROLLOVER',amt,0)) >0 or max(decode(sched_type_code,'INTCHG',amt,decode(sched_type_code,'FEEREC',amt,0))) > 0Once I replace that substitution variable in query condition with some exact test number then it works fine.
select seq_no, prod_code, descr, curr_code,
 max(decode(sched_type_code,'ROLLOVER',amt,0)) OUTSTD_DRAW,
 max(decode(sched_type_code,'INTCHG',amt,decode(sched_type_code,'FEEREC',amt,0))) OUTSTD_INTEREST_FEE
from
 select r.fac_no, r.prod_code, f.descr, r.prod_seq_no seq_no, r.curr_code, r.sched_type_code,sum(nvl(rep_amt,0)) amt
 from repay_scheds r,
 fac_prods f
 where r.fac_no = f.fac_no
 and r.prod_code = f.prd_code
 and r.prod_seq_no = f.seq_no
 and r.fac_no = 2012500
 and r.trans_ref_from is not null
 and r.status <> 'P'
 group by r.fac_no, r.prod_code, f.descr, r.prod_seq_no, r.curr_code, r.sched_type_code
group by seq_no, prod_code, descr, curr_code
having max(decode(sched_type_code,'ROLLOVER',amt,0)) >0 or max(decode(sched_type_code,'INTCHG',amt,decode(sched_type_code,'FEEREC',amt,0))) > 0How can I use substitution variable within query for "From clause query" block type? Or any other way how to get the same result?
Thanks for your reply.
Tomas

I have a solution:
Before entering block I'm calling function, that populates my block:
PROCEDURE POP_<<MY_BLOCK>>_BLOCK IS
query_txt varchar2(2000);
BEGIN
 query_txt := '(select seq_no, prod_code, descr, curr_code,
 max(decode(sched_type_code,''ROLLOVER'',amt,0)) OUTSTD_DRAW,
 max(decode(sched_type_code,''INTCHG'',amt,decode(sched_type_code,''FEEREC'',amt,0))) OUTSTD_INTEREST_FEE
 from
 select r.fac_no, r.prod_code, f.descr, r.prod_seq_no seq_no, r.curr_code, r.sched_type_code,sum(nvl(rep_amt,0)) amt
 from repay_scheds r,
 fac_prods f
 where r.fac_no = f.fac_no
 and r.prod_code = f.prd_code
 and r.prod_seq_no = f.seq_no
 and r.fac_no = '||:B2.FAC_NO||'
 and r.trans_ref_from is not null
 and r.status <> ''P''
 group by r.fac_no, r.prod_code, f.descr, r.prod_seq_no, r.curr_code, r.sched_type_code
 group by seq_no, prod_code, descr, curr_code
 having max(decode(sched_type_code,''ROLLOVER'',amt,0)) >0 or max(decode(sched_type_code,''INTCHG'',amt,decode(sched_type_code,''FEEREC'',amt,0))) > 0)';
 Go_Block('<<MY_BLOCK>>' );
 Clear_Block ;
 Set_Block_Property( '<<MY_BLOCK>>', QUERY_DATA_SOURCE_NAME, query_txt) ;
 -- populate my block --
 Execute_Query ;
END;Thanks,
Tomas

Execution of subquery of IN and EXISTS clause.

Hi Friends,
Suppose we have following two tables:
emp
empno number
ename varchar2(100)
deptno number
salary number
dept
deptno number
location varchar2(100)
deptname varchar2(100)
status varchar2(100)
Where dept is the master table for emp.
Following query is fine to me:
SELECT empno, ename
FROM emp,dept
WHERE emp.deptno = dept.deptno
AND emp.salary >=5000
AND dept.status = 'ACTIVE';
But I want to understand the behaviour of inline query (Used with IN and EXISTS clause) for which I have used this tables as an example (Just as Demo).
1)
Suppose we rewrite the above query as following:
SELECT empno, ename
FROM emp
WHERE emp.salary >=5000
AND deptno in (SELECT deptno FROM dept where status = 'ACTIVE')
Question: as shown in above query, suppose in our where clause, we have a condition with IN construct whose subquery is independent (it is not using any column of master query's resultset.). Then, will that query be executed only once or will it be executed for N number of times (N= number of records in emp table)
In other words, how may times the subquery of IN clause as in above query be executed by complier to prepared the subquery's resultset?
2)
Suppose the we use the EXISTS clause (or NOT EXISTS clause) with subquery where, the subquery uses the field of master query in its where clause.
SELECT E.empno, E.ename
FROM emp E
WHERE E.salary >=5000
AND EXISTS (SELECT 'X' FROM dept D where status = 'ACTIVE' AND D.deptno = E.deptno)
Here also, I got same confusion. For how many times the subquery for EXISTS will be executed by oracle. For one time or for N number of times (I think, it will be N number of times).
3)
I know we can't define any fix thumbrule and its highly depends on requirement and other factors, but in general, Suppose our main query is on heavily loaded large transaction table and need to check existance of record in some less loaded and somewhat smaller transaction table, than which way will be better from performance point of view from above three. (1. Use of JOIN, 2. Use of IN, 3. Use of EXISTS)
Please help me get solutions to these confusions..
Thanks and Regards,
Dipali..

Dipali,
First, I posted the links with my name only, I don;t know how did you pick another handle for addressing it?Never mind that.
>
Now another confusion I got.. I read that even if we used EXISTS and , CBO feels (from statistics and all his analysis) that using IN would be more efficient, than it will rewrite the query. My confusion is that, If CBO is smart enough to rewrite the query in its most efficient form, Is there any scope/need for a Developer/DBA to do SQL/Query tuning? Does this means that now , developer need not to work hard to write query in best menner, instade just what he needs to do is to write the query which resluts the data required by him..? Does this now mean that now no eperts are required for SQL tuning?
>
Where did you read that?Its good to see the reference which says this.I haven't come across any such thing where CBO will rewrite the query like this. Have a look at the following query.What we want to do is to get the list of all teh departments which have atleast one employee working in it.So how would be we write this query? Theremay be many ways.One,out of them is to use distinct.Let's see how it works,
SQL> select * from V$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
PL/SQL Release 11.1.0.6.0 - Production
CORE    11.1.0.6.0      Production
TNS for 32-bit Windows: Version 11.1.0.6.0 - Production
NLSRTL Version 11.1.0.6.0 - Production
SQL> set timing on
SQL> set autot trace exp
SQL> SELECT distinct D.deptno, D.dname
2        FROM     scott.dept D,scott.emp E
3 where e.deptno=d.deptno
4 order by d.deptno;
Elapsed: 00:00:00.12
Execution Plan
Plan hash value: 925733878
| Id | Operation                     | Name    | Rows | Bytes | Cost (%CPU)| T
ime     |
|   0 | SELECT STATEMENT              |         |     9 |   144 |     7 (29)| 0
0:00:01 |
|   1 | SORT UNIQUE                  |         |     9 |   144 |     7 (29)| 0
0:00:01 |
|   2 |   MERGE JOIN                  |         |    14 |   224 |     6 (17)| 0
0:00:01 |
|   3 |    TABLE ACCESS BY INDEX ROWID| DEPT    |     4 |    52 |     2   (0)| 0
0:00:01 |
|   4 |     INDEX FULL SCAN           | PK_DEPT |     4 |       |     1   (0)| 0
0:00:01 |
|* 5 |    SORT JOIN                  |         |    14 |    42 |     4 (25)| 0
0:00:01 |
|   6 |     TABLE ACCESS FULL         | EMP     |    14 |    42 |     3   (0)| 0
0:00:01 |
Predicate Information (identified by operation id):
   5 - access("E"."DEPTNO"="D"."DEPTNO")
       filter("E"."DEPTNO"="D"."DEPTNO")
SQL>
SQL> SELECT distinct D.deptno, D.dname
2        FROM     scott.dept D,scott.emp E
3 where e.deptno=d.deptno
4 order by d.deptno;
    DEPTNO DNAME
        10 ACCOUNTING
        20 RESEARCH
        30 SALES
Elapsed: 00:00:00.04
SQL>So CBO did what we asked it do so.It made a full sort merge join.Now there is nothing wrong in it.There is no intelligence added by CBO to it.So now what, the query looks okay isn't it.If the answer is yes than let's finish the talk here.If no than we proceed further.
We deliberately used the term "atleast" here.This would govern that we are not looking for entirely matching both the sources, emp and dept.Any matching result should solve our query's result.So , with "our knowledge" , we know that Exist can do that.Let's write teh query by it and see,
SQL> SELECT   D.deptno, D.dname
2        FROM     scott.dept D
3          WHERE    EXISTS
4                 (SELECT 1
5                  FROM   scott.emp E
6                  WHERE E.deptno = D.deptno)
7        ORDER BY D.deptno;
    DEPTNO DNAME
        10 ACCOUNTING
        20 RESEARCH
        30 SALES
Elapsed: 00:00:00.00
SQL>Wow, that's same but there is a small difference in the timing.Note that I did run the query several times to elliminate the physical reads and recursive calls to effect the demo. So its the same result, let's see the plan.
SQL> SELECT   D.deptno, D.dname
2        FROM     scott.dept D
3          WHERE    EXISTS
4                 (SELECT 1
5                  FROM   scott.emp E
6                  WHERE E.deptno = D.deptno)
7        ORDER BY D.deptno;
Elapsed: 00:00:00.00
Execution Plan
Plan hash value: 1090737117
| Id | Operation                    | Name    | Rows | Bytes | Cost (%CPU)| Ti
me     |
|   0 | SELECT STATEMENT             |         |     3 |    48 |     6 (17)| 00
:00:01 |
|   1 | MERGE JOIN SEMI             |         |     3 |    48 |     6 (17)| 00
:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| DEPT    |     4 |    52 |     2   (0)| 00
:00:01 |
|   3 |    INDEX FULL SCAN           | PK_DEPT |     4 |       |     1   (0)| 00
:00:01 |
|* 4 |   SORT UNIQUE                |         |    14 |    42 |     4 (25)| 00
:00:01 |
|   5 |    TABLE ACCESS FULL         | EMP     |    14 |    42 |     3   (0)| 00
:00:01 |
Predicate Information (identified by operation id):
   4 - access("E"."DEPTNO"="D"."DEPTNO")
       filter("E"."DEPTNO"="D"."DEPTNO")Can you see a keyword called Semi here? This means that Oralce did make an equi join but not complete.Compare the bytes/rows returned from this as well as cost with the first query.Can you notice the difference?
So what do we get from all this?You asked that if CBO becomes so smart, won't we need developers/dbas at that time?The answer is , what one wants to be, a monkey or an astranaut? Confused,read this,
http://www.method-r.com/downloads/doc_download/6-the-oracle-advisors-from-a-different-perspective-karen-morton
So it won't matter how much CBO would become intelligent, there will be still limitations to where it can go, what it can do.There will always be a need for a human to look all the automations.Rememember even the most sofisticated system needs some button to be pressed to get it on which is done by a human hand's finger ;-).
Happy new year!
HTH
Aman....

Is there a way to use dynamic built string in the "from" clause

Hi all, im having one problem and now, im not sure how to solve it easily at all... :) Is there someone that would be so kind and put a eye on it? ..thx
I have plsql proc, in which i have a list of table_names. For each of that table i need to run a query that will retrieve me a list of values and for each of that value i need to do something.
If i can be more specific about the problem -> each of that table is built as key_column, value_columns, day,starttime. For a key per table there are 4 records per hour - every quarter. Im truncating those quarters to full-quarter (minutes => 0->14 = 0min; 15->29 = 15min, 30->44 = 30, 45->59=45)
example
i get for one key and specific hour four records at 15:01;15:16;15:31;15:46 => i truncate em to 15:00;15:15;15:30;15:45..Sometimes there is a problem with the tool that is generating those data for me, and one quarter could be moved a little - so i get data like 15:01;15:16;15:29;15:46 => after i truncate the times i get duplicates in second quarter. It also can happen like this : 23:00; 23:14; 23:29; 23:44; 23:59 => totaly bad => cos the last one supposed to be as 0:00 next day, ..and 23:14 as 23:15...So...that was a problem - and solution -> i wanted to create plsql that will find those hours in each table i ve defined, and for each problem hour i make some fixes - update the bad time ...
..and i have problem - can i put an dynamic built table_name in the "from" clause?
example how i wanted to do that:
declare
     type t_objectName     is table of varchar2(030) index     by pls_integer;
     l_tableName              t_objectName;
begin
l_tableName(1) := 'tmphlrgl';
l_tableName(2) := 'tmprcfgl';
l_tableName(3) := 'tmprcfbs';
l_tableName(4) := 'tmpvlrgl';
for i in (select evtime from (select day,trunc_quarter(evtime) evtime,m_id from l_tableName(i) group by day,trunc_quarter(evtime),m_id having count(*)>1) order by evtime) loop
--some other conditions and the update...
end loop;
end;
/I cannot use the l_tableName(i) for FROM ...get an error...I was thinking to build it as dynamic sql and execute immediate into some kind of object that can store mutliple lines, from which i would in the FOR cycle get the data...But im not sure if this could be done in plsql...
thanks for your time and help..
d.

declare
c sys_refcursor;
begin
for i in 1..4 loop
open c for 'day,trunc_quarter(evtime) evtime,m_id
from ' || l_tableName(i) ||
'group by day,trunc_quarter(evtime),m_id having
count(*)>1) order by evtime';Just to high light SELECT is missing that all
OPEN c FOR ' SELECT day,trunc_quarter(evtime) evtime,m_id
          FROM' || l_tableName(i) ||
'GROUP BY day,trunc_quarter(evtime),m_id HAVING count(*)>1)   ORDER BY evtime';

Is it possible to create a view where table in the From clause changes name

is it possible to create a view from a from a table like this
create view my_view as select id, col1, col2, result from <<my_latest_cacahe_table>>;
the table in the from clause changes the name .
I have another table which indicates the the latest name of my cache tables. Always there are two records there. The latest one and previous one.
select * from cache_table_def
table_name cache_table_name refresh_date
my_table cache_table245 1/23/2012
my_table cache_table235 1/22/2012
create table cache_table_def (table_name varchar2(25), cache_table_name varchar2(25), refresh_date date);
insert into cache_table_def values( 'my_table','cache_table245','23-jan-2012');
insert into cache_table_def values ( 'my_table','cache_table546','22-jan-2012');
create table cache_table245 (id number, col1 varchar2(50), col2 varchar2(20), result number);
insert into cache_table245 values(1, 'test123', 'test345',12.12);
insert into cache_table245 values (2, 'test223', 'test245',112.12);
create table cache_table235 (id number, col1 varchar2(50), col2 varchar2(20), result number);
insert into cache_table235 values (1, 'test123', 'test345',92.12);
insert into cache_table235 values (2, 'test223', 'test245',222.12);
what I need to do is find the latest cache_table name for my_table and use that in my view defintion
When user select from the the view it always reurns the data from the latest cache_table
is it possible to do something like this in oracle 11g?
I have no control on the cache tables names. that is why I need to use the latest name from the table.
Any ideas really appreciated.

I've worked up an example that does what you ask. It uses the SCOTT schema EMP table. Make two copies of the EMP table, EMP1 and EMP2. I deleted dept 20 from emp1 and deleted dept 30 from emp2 so I could see that the result set really came from a different table.
-- create a context to hold an environment variable - this will be the table name we want the view to query from
create or replace context VIEW_CTX using SET_VIEW_FLAG;
-- create the procedure specified for the context
- we will pass in the name of the table to query from
create or replace procedure SET_VIEW_FLAG ( p_table_name in varchar2 default 'EMP')
as
begin
dbms_session.set_context( 'VIEW_CTX', 'TABLE_NAME', upper(p_table_name));
end;
-- these are the three queries - one for each table - none of them will return data until you set the context variable.
select * from emp where 'EMP' = sys_context( 'VIEW_CTX', 'TABLE_NAME' );
select * from emp1 where 'EMP1' = sys_context( 'VIEW_CTX', 'TABLE_NAME' );
select * from emp2 where 'EMP2' = sys_context( 'VIEW_CTX', 'TABLE_NAME' )
-- this is how you set the context variable depending on the table you want the view to query
exec set_view_flag( p_table_name => 'EMP' );
exec set_view_flag( p_table_name => 'EMP1' );
exec set_view_flag( p_table_name => 'EMP2');
-- this will show you the current value of the context variable
SELECT sys_context( 'VIEW_CTX', 'TABLE_NAME' ) FROM DUAL
-- this is the view definition - it does a UNION ALL of the three queries but only one will actually return data
CREATE VIEW THREE_TABLE_EMP_VIEW AS
select * from emp where 'EMP' = sys_context( 'VIEW_CTX', 'TABLE_NAME' )
union all
select * from emp1 where 'EMP1' = sys_context( 'VIEW_CTX', 'TABLE_NAME' )
union all
select * from emp2 where 'EMP2' = sys_context( 'VIEW_CTX', 'TABLE_NAME' )
-- first time - no data since context variable hasn't been set yet
SELECT * FROM THREE_TABLE_EMP_VIEW
-- get data from the EMP table
exec set_view_flag( p_table_name => 'EMP' );
SELECT * FROM THREE_TABLE_EMP_VIEW
-- get data from the EMP2 table
exec set_view_flag( p_table_name => 'EMP2');
SELECT * FROM THREE_TABLE_EMP_VIEW
For your use case you just have to call the context procedure whenever you want to switch tables. You can union all as many queries as you want and can even put WHERE clause conditions based on other filtering criteria if you want. I have used this approach with report views so that one view can be used to roll up report data different ways or for different regions, report periods (weekly, quarterly, etc). I usually use this in a stored procedure that returns a REF CURSOR to the client. The client requests a weekly report and provides a date, the procedure calculates the START/END date based on the one date provided and sets context variables that the view uses in the WHERE clause for filtering.
For reporting it works great!

CAN I PASS A TABLE NAME AS A VARIABLE IN THE FROM CLAUSE?

For some reason, I am trying to use a variable name containing the actual table name in the from clause and it won't allow me. I keep getting the error saying I need to declare the variable I'm using eventhough I've used it in another statement that is not the FROM clause.
Example
SELECT count(col1), sum(col2)
FROM v_table_name;
v_table_name was declared as:
v_tablename VARCHAR2(20);
v_tablename := real_table_name;
Is it not allowed to use variables in the FROM clause or am I missing something here?

You can use the Forms "From Clause Query" as the datasource for the data block. Then you can change the QUERY_DATA_SOURCE_NAME using set_block_property, so you can use any SQL statement you like. Of course you must name/alias the columns in a consistent manner so that the number of database items on the block matches those being queried.

Error while using REMAP_TABLE and WHERE clause together in IMPDP

I am trying to move some records from a very large table to another small table.
I am facing trouble while using REMAP_TABLE and WHERE clause together in IMPDP.
Problem is data filter is not getting applied and all records are getting imported.
here is how I have simulated this. please advice.
CREATE TABLE TSHARRHB.TMP1
A NUMBER,
B NUMBER
begin
Insert into TSHARRHB.TMP1
   (A, B)
Values
   (1, 1);
Insert into TSHARRHB.TMP1
   (A, B)
Values
   (2, 2);
COMMIT;
end;
expdp system/password TABLES=tsharrhb.TMP1 DIRECTORY=GRDP_EXP_DIR DUMPFILE=TMP1.dmp REUSE_DUMPFILES=YES LOGFILE=EXP.log PARALLEL=8
impdp system/password DIRECTORY=GRDP_EXP_DIR DUMPFILE=TMP1.dmp LOGFILE=imp.log PARALLEL=8 QUERY='TSHARRHB.TMP1:"WHERE TMP1.A = 2"' REMAP_TABLE=TSHARRHB.TMP1:TMP3 CONTENT=DATA_ONLY
Import: Release 11.2.0.1.0 - Production on Fri Dec 13 05:13:30 2013
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Automatic Storage Management, OLAP, Data Mining
and Real Application Testing options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01": system/********@GRD6.RBSG DIRECTORY=GRDP_EXP_DIR DUMPFILE=TMP1.dmp LOGFILE=SSD_93_TABLES_FULL_EXP.log PARALLEL=8 QUERY=TSHARRHB.TMP1:"WHERE TMP1.A = 2" REMAP_TABLE=TSHARRHB.TMP1:TMP3 CONTENT=DATA_ONLY
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "TSHARRHB"."TMP3"                           5.421 KB       2 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" successfully completed at 05:13:33
here I am expecting only 1 record to get imported but both the records are getting imported. please advice.

The strange thing compared to your output is that I get an error when I have table prefix in the query block:
Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01": system/******** DUMPFILE=TMP1.dmp LOGFILE=imp.log PARALLEL=8 QUERY=SYSADM.TMP1:"WHERE TMP1.A = 2" REMAP_TABLE=SYSADM.TMP1:TMP3 CONTENT=DATA_ONLY
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
ORA-31693: Table data object "SYSADM"."TMP3" failed to load/unload and is being skipped due to error:
ORA-38500: Unsupported operation: Oracle XML DB not present
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 1 error(s) at Fri Dec 13 10:39:11 2013 elapsed 0 00:00:03
And if I remove it, it works:
Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01": system/******** DUMPFILE=TMP1.dmp LOGFILE=imp.log PARALLEL=8 QUERY=SYSADM.TMP1:"WHERE A = 2" REMAP_TABLE=SYSADM.TMP1:TMP3 CONTENT=DATA_ONLY
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "SYSADM"."TMP3"                             5.406 KB       1 out of 2 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" successfully completed at Fri Dec 13 10:36:50 2013 elapsed 0 00:00:01
Nicolas.
PS: as you can see, I'm on 11.2.0.4, I do not have 11.2.0.1 that you seem to use.

SELECT statement in FROM clause - syntax help

Hi,
I want to have a SELECT statement in the FROM clause. I get syntax error when doing this and since I am new to ABAP I need som help.
I want to do the following, (and if anyone has any SELECT statement from their own system which you know there is no syntax error in please post it here so I can analyze the syntax):
*I leave the INTO itab clause out, since I only want to demonstrate the functionality
I am trying to get.
SELECT tableOne~someField
FROM tab AS tableOne (SELECT someField
 FROM tab
 WHERE someFiled > 1) AS tableTwo
WHERE tableOnesomeField > tableTwosomeField
like I said, the problem is that the select statement in the parenthesis in the from clause seems to be incorrect because I get "wrong expression" when trying to compile. Is this because I cannot have a select statement in the from clause or is it because of a minor syntax error, such as I forgot a dot, or some other sign?
thanks and regards
Baran

sorry i am not enough familiar with sub queries but some error i can see which i will state here.
1> you have to use sub queries i.e. select in ( ) after where clause because here you are fulfilling a where clause by another select statement.
like this
SELECT * FROM SFLIGHT
 INTO WA
 WHERE SEATSOCC = ( SELECT MAX( SEATSOCC ) FROM SFLIGHT ).
2> you cannot specify field name without into clause either you have to use
select * or select f1 into tab-f1 like this...
but if you are using select * without into you have to define
tables : dbtab.
selec * from dbtab. like that.
regards
shiba dutta

Can't get query to work. table alias in subquery in FROM clause

How can I rearrange this query to work?
SELECT
 TO_CHAR(dt.date_time, 'YYYY-MM-DD') start_date,
 (SELECT COUNT(*) FROM
 (SELECT DISTINCT a.non_asp, a.start_time, a.end_time
 FROM appointments a
 WHERE a.start_time >= dt.date_time AND a.start_time < dt.date_time + 1
 ) num_overlap
 FROM
 table(times_pkg.between_times(TO_DATE('2010-05-30'),
 TO_DATE('2010-07-03'), 60*24, 'Y')) dtbetween_times is a table function that returns times at given intervals.
I am trying to get a count of distinct (non_asp, start_time, end_time) sets that fall on each day.
However, it doesn't recognize dt.date_time in the FROM clause.

Hi,
A sub-query can be correlated only to its immediate parent. You're trying the correlate the SELECT DISTINCT sub-query to its grandparent.
You can re-write the sub-query as a join, like this:
SELECT TO_CHAR(dt.date_time, 'YYYY-MM-DD') start_date,
 a.num_overlap
FROM table ( times_pkg.between_times ( TO_DATE('2010-05-30'),
 TO_DATE('2010-07-03'),
 60*24,
 'Y'
 ) dt
JOIN (
 SELECT start_time,
 end_time,
 COUNT (DISTINCT non_asp) AS num_overlap
 FROM appointments
 ) a ON a.start_time >= dt.date_time
 AND a.start_time < dt.date_time + 1
;You could also eliminate the extra level between the SELECT DISTINCT sub-query and the main query by using SELECT (DISTINCT ...).

CBO and FROM clause

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