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Full Discussion: Optimizing query
Special Forums UNIX and Linux Applications Optimizing query Post 302130292 by jim mcnamara on Saturday 4th of August 2007 06:34:25 PM
Old 08-04-2007
Look - the query has to search the ENTIRE output of the IN (SELECT ..)
for each set of rows it deletes. I know that rowid's are what you get from an index.

Instead of me going on about this - look in Tom Kyte's book 'EXpoert One on One' and look in the analytical function chapter - there is an example of how to optimize a query very like this. Or try the asktom oracle site:
From there:
Code:
from 
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1224636375004

delete from tableA a
     where rowid <> ( select max(rowid)
                        from tableA b 
                       where b.column1 = a.column1)
    /

 

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IFX_AFFECTED_ROWS(3)							 1						      IFX_AFFECTED_ROWS(3)

ifx_affected_rows - Get number of rows affected by a query

SYNOPSIS
int ifx_affected_rows (resource $result_id) DESCRIPTION
Returns the number of rows affected by a query associated with $result_id. For inserts, updates and deletes the number is the real number (sqlerrd[2]) of affected rows. For selects it is an estimate (sqlerrd[0]). Don't rely on it. The database server can never return the actual number of rows that will be returned by a SELECT because it has not even begun fetching them at this stage (just after the "PREPARE" when the optimizer has determined the query plan). Useful after ifx_prepare(3) to limit queries to reasonable result sets. PARAMETERS
o $result_id - A valid result id returned by ifx_query(3) or ifx_prepare(3). RETURN VALUES
Returns the number of rows as an integer. EXAMPLES
Example #1 Informix affected rows <?php $rid = ifx_prepare("select * from emp where name like " . $name, $connid); if (! $rid) { /* ... error ... */ } $rowcount = ifx_affected_rows($rid); if ($rowcount > 1000) { printf ("Too many rows in result set (%d) <br />", $rowcount); die ("Please restrict your query<br /> "); } ?> SEE ALSO
ifx_num_rows(3). PHP Documentation Group IFX_AFFECTED_ROWS(3)
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