Are Explicit Cursors better than Select Statement

Hi Gurus,
I came across this opinion that explicit cursors are better (even if the query returns a single row) instead of a single row SELECT statement within the code in terms of performance.
Is that true??? Pls elaborate in either case.
Can i hear it from Sri/Andrew ???
Thanks for ur time...
Peyush

no, it is just the opposite
see
http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:1205168148688
for a complete explanation why
greetings
Freek
Hi Gurus,
I came across this opinion that explicit cursors are better (even if the query returns a single row) instead of a single row SELECT statement within the code in terms of performance.
Is that true??? Pls elaborate in either case.
Can i hear it from Sri/Andrew ???
Thanks for ur time...
Peyush

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Use of cursors insted of select statements

could any one please explain what is the advantage of using cursors instead of simple select statements
thanks
siby

A benefit to using an explicit cursor rather than a select statement, is for the NO_DATA_FOUND exception. Its kind of like a free IF statment. IF no data is found, then stop.
if you write a select statement, and no data is returned, you SHOULD code for the NO_DATA_FOUND exception. Often people say, "i'll ALWAYS get a row returned". but you should always cover your code "just in case". so you must code an exception...
declare
v_var varchar2(1);
procedure do_something(p_parm varchar2) is
begin
null;
end do_something;
procedure log_error is
begin
null;
end log_error;
begin <<main>>
do_something('x');
begin <<selectblock>>
select dummy
into v_var
from dual
where dummy = 'a';
do_something(v_var);
exception
when no_data_found then
log_error;
end selectblock;
do_something (v_var||'abc');
end main;
if you use an explicit cursor instead, you don't need to code for the NO_DATA_FOUND. If an explicit cursor opens and finds no rows, there are simply no rows. of course, you don't need a loop if you expect only 1 row returned under normal circumstances.
BTW, don' forget that SQL%ROWCOUNT and your_cursor%ROWCOUNT are not initialized. There is a null, until a row is successfully fetched. therefore if no rows are returned at all, %ROWCOUNT is NULL.
declare
v_var varchar2(1);
cursor my_cur is
select dummy
from dual
where dummy = 'a';
procedure do_something(p_parm varchar2) is
begin
null;
end do_something;
procedure log_error is
begin
null;
end log_error;
begin << main>>
for cur_rec in my_cur loop
dbms_output.put_line('inside');
begin <<loop_block>>
if nvl(my_cur%rowcount,0) > 1 then
do_something(cur_rec.dummy);
else
log_error;
end if;
end loop_block;
end loop;
end main;
/

Is it better to use bapi_salesorder_getlist than select statements?

hi experts,
in terms of performance, which is better in getting a list of salesorders is it better bapi_salesorder_getlist or select statements?
for bapi_salesorder_getlist, i will not get all of the fields so i would still use select.
Message was edited by:
maui bayog

Hi,
If ur requiremetn is specific and can be solved using bapi_salesorder_getlist then only use it, otherwise, use select stament which is more useful for reports as it gives o/p as required and not a predefined limited output. Now u may get sufficient fields but , in future if requirement will change then for small change u may be in problem.
Bapis are very userful for specifc and limited tasks.
Jogdand M B

Why are two queries better than one

I'm trying to help out our developers who are struggling with the performance of a very simple select statmenent that for some reason is exhibiting some very inexplicable results.
I'll show the SQL as a single statement first.....
select * from transaction1 t where t.hid in (select distinct h.hid from history1 h,filter1 f where h.fid = f.fid and f.match='value');
transaction 1 has 250k records, history1 has about 100k as does filter1. We know generally the subselect will only return a total of half a dozen or less records (only 1 in our testing here).
Running the above query takes around 7 seconds.
Changing this to a with clause.....
WITH a as (select distinct h.hid from history1 h,filter1 f where h.fid = f.fid and f.match='value') select * from transaction1 t where t,hid in (select a.hid from a);
and the runtime drops to 3 seconds. But then re-running the first statement again also now takes 3 seconds (so I guess there's some caching going on there).
Now what really puzzles is if we split this into two queries.....
select distinct h.hid from history1 h,filter1 f where h.fid = f.fid and f.match='value';
This takes .1 of a second,
select * from transaction1 t where t.hid in (12345);
And this takes .1 of a second.
So why when run seperately are they so fast, yet combined they take so long. I'm a bit baffled by this. We've rewritten the same SQL in half a dozen different ways with the same result and also done the same thing with other tables as well. Is it an optimisation issue?

Appologies for not following protocol, my first time posting on here.
Oracle 10g clustered.
We have limited access as it's a customers server, but the explain plan comes back as....
PLAN_TABLE_OUTPUT
Plan hash value: 898894568
| Id | Operation            | Name              | Rows | Bytes | Cost (%CPU)|Time     |
PLAN_TABLE_OUTPUT
|   0 | SELECT STATEMENT     |                   | 49553 |    37M| 7075   (2)|00:01:25 |
|* 1 | HASH JOIN RIGHT SEMI|                   | 49553 |    37M| 7075   (2)|00:01:25 |
|   2 |   VIEW               | VW_NSO_1          | 26131 |   331K|   476   (4)|00:00:06 |
|* 3 |    HASH JOIN         |                   | 26131 |   791K|   476   (4)|00:00:06 |
PLAN_TABLE_OUTPUT
|* 4 |     TABLE ACCESS FULL| FILTER1           | 26131 |   484K|   246   (4)|00:00:03 |
|   5 |     TABLE ACCESS FULL| HISTORY1          |   104K| 1225K|   227   (3)|00:00:03 |
|   6 |   TABLE ACCESS FULL | TRANSACTION1      |   199K|   150M| 6593   (1)|00:01:20 |
PLAN_TABLE_OUTPUT
Predicate Information (identified by operation id):
   1 - access("T"."TID"="$nso_col_1")
   3 - access("H"."HID"="F"."ID")
   4 - filter("F"."MATCH"='value')
20 rows selectedI'll admit, I'm not completely clear on what I'm reading here, other than the fact there are some big differences in the timing values
We don't have privaleges to run trace, so I'm a bit stuffed there as I'm on the clients site, however I will get my developers to try this on our local server.
Edited by: user1410957 on 15-Sep-2009 06:14

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If you have 2 drives: 1 for the boot and the other for data:
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Anyhow, I have recently moved and want to connect my computer to the optimum online (the long island version of road runner) modem. However, I need a router, because cablevision is too cheap to provide one (even though Verizon does for their DSL service, and it's about 60% of the cost of time warner, but that's not why I'm here...haha). I actually have a few questions regarding this issue.
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Jeremy, First welcome to the discussions,
Wireless technology is just a few mbs slower than a wired connection, for the most part you won't notice it.
Cabble is different than DSL. With cable you will get better more consistant speeds than you will with DSL.
Normally DSL is furnished through phone lines and the farther you are from the ISP's Servers the slower your connection is. This is not the case with Cable.
You are correct about Viruses. Mac is not to date affected by viruses Trojans and Malware. It is a good idea if for no other reason than peace of mind to have Virex or
http://www.clamxav.com/
All ISp's have firewalls on there servers, as well as any Router you buy will have a Firewall that is normally configured by typing in 192.168.1.1 in your Browser this will open the Routers Utility settings. This information is with any Routers Paperwork.
Mac OSX has one of the best firewalls you can also set up.
Normally almost all Viruses are sent through e-mail while they won't affect the UNIX operating system when you get an e-mail with a virus you can pass it on to another windows user who can be infected.
If you have the adapter that plugs in to the socket that accepts the Cable in and the Cat5 or Cat6 out then yes you can use it, you will need the Ip Address that your service provides. If your serviceuses Cat 5 or 6 Eternet Cable the technology is the same worldwide. It really depends on what your cable service has furnished you with.
You should be able to run an ethernet cable from your Internet Service Providers Modem ( Instead of plugging it in to your computer) Plug it into the Uplink port of the Verizon Router and try it. Like I said you may have to get into the Utility and set the Ip for you to do away with the other one, you should only need one.
It would however be the hot set up if you can use the Modem Router Combined.
There is also a good chance if they haven't hooked you up yet show the tech that comes to hook you up the Modem Router you have and if he can he will probably use it if you talk real nice.
Remember for the most part a Modem is a Modem, and a Router is a Router. Some have a few different features but the technology is the same and works under the same principles.
This should help. Don

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Using Cursor in Select statements? How to do this?

I am getting an error whilt passing a cursor to a select clause:
SELECT dbms_xmlquery.getXML('select deptno, dname, '||
'cursor(select empno, ename, sal from emp e where e.deptno = d.deptno) employees '||
'from dept d where d.deptno in (10, 20)')
FROM dual;
DBMS_XMLQUERY.GETXML('SELECTDEPTNO'||'CURSORIS(SELECTEMPNOFROMEMPEWHEREE.DEPT=D.
<?xml version = '1.0'?>
<ERROR>oracle.xml.sql.OracleXMLSQLException: ORA-00923
: FROM keyword not found where expected
</ERROR
THIS IS DUE TO THE CURSOR AND ITS FROM STATEMENT?
CAN ANY ONE PLEASE GUIDE AS TO HOW TO USE CURSORS IN A SELECT STATEMENT PLEASE?

Another duplicate thread. See my response Select CLAUSE error using CURSORS & XSU.Please SEE..
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How to pass values in select statement as a parameter?

Hi,
Very simple query, how do I pass the values that i get in the cursor to a select statement. If table1 values are 1,2,3,4 etc , each time the cursor goes through , I will get one value in the variable - Offer
So I want to pass that value to the select statement.. how do i do it?
the one below does not work.
drop table L1;
create table L1
(col1 varchar(300) null) ;
insert into L1 (col1)
select filter_name from table1 ;
SET SERVEROUTPUT ON;
DECLARE
offer table1.col1%TYPE;
factor INTEGER := 0;
CURSOR c1 IS
SELECT col1 FROM table1;
BEGIN
OPEN c1; -- PL/SQL evaluates factor
LOOP
FETCH c1 INTO offer;
EXIT WHEN c1%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(offer);
select * from table1 f where f.filter_name =:offer ;
factor := factor + 1;
DBMS_OUTPUT.PUT_LINE(factor);
END LOOP;
CLOSE c1;
END;

Hi User,
You are looking somethuing like this, as passing the values to the Cursor as a Paramter.
DECLARE
   CURSOR CURR (V_DEPT IN NUMBER)    --- Cursor Declaration which accepts the deptno as parameter.
   IS
      SELECT *
        FROM EMP
       WHERE DEPTNO = V_DEPT;    --- The, Input V_DEPT is passed here.
   L_EMP   EMP%ROWTYPE;
BEGIN
   OPEN CURR (30);       -- Opening the Cursor to Process the Value for Department Number 30 and Processing it with a Loop below.
   DBMS_OUTPUT.PUT_LINE ('Employee Details for Deptno:30');
   LOOP
      FETCH CURR INTO L_EMP;
      EXIT WHEN CURR%NOTFOUND;
      DBMS_OUTPUT.PUT ('EMPNO: ' || L_EMP.EMPNO || ' is ');
      DBMS_OUTPUT.PUT_LINE (L_EMP.ENAME);
   END LOOP;
   CLOSE CURR;
   DBMS_OUTPUT.PUT_LINE ('Employee Details for Deptno:20'); -- Opening the Cursor to Process the Value for Department Number 20
   OPEN CURR (20);
   LOOP
      FETCH CURR INTO L_EMP;
      EXIT WHEN CURR%NOTFOUND;
      DBMS_OUTPUT.PUT ('EMPNO: ' || L_EMP.EMPNO || ' is ');
      DBMS_OUTPUT.PUT_LINE (L_EMP.ENAME);
   END LOOP;
   CLOSE CURR;
END;Thanks,
Shankar

Passing value as a parameter in select statement

Hi,
Very simple query, how do I pass the values that i get in the cursor to a select statement. If table1 values are 1,2,3,4 etc , each time the cursor goes through , I will get one value in the variable - Offer
So I want to pass that value to the select statement.. how do i do it?
the one below does not work.
drop table L1;
create table L1
(col1 varchar(300) null) ;
insert into L1 (col1)
select filter_name from table1 ;
SET SERVEROUTPUT ON;
DECLARE
offer table1.col1%TYPE;
factor INTEGER := 0;
CURSOR c1 IS
SELECT col1 FROM table1;
BEGIN
OPEN c1; -- PL/SQL evaluates factor
LOOP
FETCH c1 INTO offer;
EXIT WHEN c1%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(offer);
select * from table1 f where f.filter_name =:offer ;
factor := factor + 1;
DBMS_OUTPUT.PUT_LINE(factor);
END LOOP;
CLOSE c1;
END;

Hi Greg,
Thanks for the response, No there is no ODB.net involved here.
If I remove the : from :offer. I get this error now.
Changed SQL is:
select * from table1 f where f.filter_name =offer ;
Error report:
ORA-06550: line 16, column 23:
PL/SQL: ORA-00942: table or view does not exist
ORA-06550: line 16, column 9:
PL/SQL: SQL Statement ignored
06550. 00000 - "line %s, column %s:\n%s"
*Cause: Usually a PL/SQL compilation error.
*Action:

Dynamic Parameter LOV Select Statement

I have a parameter form with a value for the fiscal year and equipment ID. I want to populate the equipment ID list of values based on the fiscal year that is selected.
My query for the equipment ID list of values would be SELECT EQPID,NAME FROM EQPLIST WHERE FY = :FY.
When I tried to add this query to the list of values of the equipment ID parameter I get REP-0781: Bind variables are not allowed in the Select statement.
Is there a way to dynamically generate the list of values select statement in a reports trigger?

Hi,
What version of Oracle Reports are you using?
Unfortunately, it is a limitation of Oracle Reports to not restrict values based on other parameters - for sure until Reports 6i and I believe until the recent new versions.
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Venkat

Are Explicit Cursors better than Select Statement

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