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Top Forums Programming Getting Rows from a MySQL Table with max values? Post 302633841 by Corona688 on Wednesday 2nd of May 2012 02:03:10 PM
Old 05-02-2012
I'm not saying a full table-scan will happen as much as, the result of an indexed query can't be different than what a table scan could do. (Except in order, which isn't guaranteed anyway, ORDER BY sorts after the fact.) Therefore, it won't use information from the index to know the maximum in advance. Your second query, where you just 'select max(..) from ...' would be able to use the index.

I'm not sure index is required either, as much as the performance could be quite poor if it isn't.
 

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Apache::Session::Store::MySQL(3pm)			User Contributed Perl Documentation			Apache::Session::Store::MySQL(3pm)

NAME
Apache::Session::Store::MySQL - Store persistent data in a MySQL database SYNOPSIS
use Apache::Session::Store::MySQL; my $store = new Apache::Session::Store::MySQL; $store->insert($ref); $store->update($ref); $store->materialize($ref); $store->remove($ref); DESCRIPTION
Apache::Session::Store::MySQL fulfills the storage interface of Apache::Session. Session data is stored in a MySQL database. SCHEMA
To use this module, you will need at least these columns in a table called 'sessions', or another table name if you provide the TableName argument: id char(32) # or however long your session IDs are. a_session text To create this schema, you can execute this command using the mysql program: CREATE TABLE sessions ( id char(32) not null primary key, a_session text ); If you use some other command, ensure that there is a unique index on the table's id column. CONFIGURATION
The module must know what datasource, username, and password to use when connecting to the database. These values can be set using the options hash (see Apache::Session documentation). The options are: DataSource UserName Password TableName Handle Example: tie %hash, 'Apache::Session::MySQL', $id, { DataSource => 'dbi:mysql:database', UserName => 'database_user', Password => 'K00l', TableName => 'sessions' }; Instead, you may pass in an already-opened DBI handle to your database. tie %hash, 'Apache::Session::MySQL', $id, { Handle => $dbh }; AUTHOR
This modules was written by Jeffrey William Baker <jwbaker@acm.org> SEE ALSO
Apache::Session perl v5.10.1 2010-10-18 Apache::Session::Store::MySQL(3pm)
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