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Full Discussion: Optimizing query
Special Forums UNIX and Linux Applications Optimizing query Post 302130445 by kahuna on Monday 6th of August 2007 09:06:11 AM
Old 08-06-2007
I made a test table with a single varchar field and no index. I loaded it with 30,000 records and an additional 30 duplicate records. I ran the following queries.

Code:
select count(*) FROM tableA
WHERE rowid not in
(SELECT MIN(rowid) FROM tableA GROUP BY column1);

1 hour 12 minutes 58 seconds

Code:
select count(*) FROM tableA A1
WHERE column1 in (SELECT column1 FROM tableA GROUP BY column1 having count(*)
> 1)
and rowid != (select min(rowid) from tableA A2 where A1.column1 = A2.column1);

1 second

Code:
select count(*) from tableA a
     where rowid <> ( select max(rowid)
                        from tableA b
                       where b.column1 = a.column1);

6 min 29 sec

Your mileage may vary.

Last edited by kahuna; 08-06-2007 at 11:04 AM..
 

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CUBRID_UNBUFFERED_QUERY(3)						 1						CUBRID_UNBUFFERED_QUERY(3)

cubrid_unbuffered_query - Perform a query without fetching the results into memory

SYNOPSIS
resource cubrid_unbuffered_query (string $query, [resource $conn_identifier]) DESCRIPTION
This function performs a query without waiting for that all query results have been complete. It will return when the results are being generated. PARAMETERS
o $query -A SQL query. o $conn_identifier -The CUBRID connection. If the connection identifier is not specified, the last connection opened by cubrid_connect(3) is assumed. RETURN VALUES
For SELECT, SHOW, DESCRIBE or EXPLAIN statements returns a request identifier resource on success. For other type of SQL statements, UPDATE, DELETE, DROP, etc, returns TRUE on success. FALSE on failure. NOTES
Note The benefits of cubrid_unbuffered_query(3) come at a cost: you cannot use cubrid_num_rows(3) and cubrid_data_seek(3) on a result set returned from cubrid_unbuffered_query(3). EXAMPLES
Example #1 cubrid_unbuffered_query(3) example <?php $link = cubrid_connect("localhost", 30000, "demodb", "dba", ""); if (!$link) { die('Could not connect.'); } $query = "select * from code"; $result = cubrid_unbuffered_query($query, $link); while ($row = cubrid_fetch($result)) { var_dump($row); } cubrid_close_request($result); cubrid_disconnect($link); ?> PHP Documentation Group CUBRID_UNBUFFERED_QUERY(3)
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