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POWhy does MySQL not use an index for a greater than comparison?
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copied!<p>I am trying to optimize a bigger query and ran into this wall when I realized this part of the query was doing a full table scan, which in my mind does not make sense considering the field in question is a primary key. I would <em>assume</em> that the MySQL Optimizer would use the index.</p> <p>Here is the table:</p> <pre><code> CREATE TABLE userapplication ( application_id int(11) NOT NULL auto_increment, userid int(11) NOT NULL default '0', accountid int(11) NOT NULL default '0', resume_id int(11) NOT NULL default '0', coverletter_id int(11) NOT NULL default '0', user_email varchar(100) NOT NULL default '', account_name varchar(200) NOT NULL default '', resume_name varchar(255) NOT NULL default '', resume_modified datetime NOT NULL default '0000-00-00 00:00:00', cover_name varchar(255) NOT NULL default '', cover_modified datetime NOT NULL default '0000-00-00 00:00:00', application_status tinyint(4) NOT NULL default '0', application_created datetime NOT NULL default '0000-00-00 00:00:00', application_modified timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP, publishid int(11) NOT NULL default '0', application_visible int(11) default '1', PRIMARY KEY (application_id), KEY publishid (publishid), KEY application_status (application_status), KEY userid (userid), KEY accountid (accountid), KEY application_created (application_created), KEY resume_id (resume_id), KEY coverletter_id (coverletter_id), ) ENGINE=MyISAM ; </code></pre> <p>This simple query seems to do a full table scan:</p> <pre><code>SELECT * FROM userapplication WHERE application_id > 1025;</code></pre> <p>This is the output of the EXPLAIN:</p> <pre> +----+-------------+-------------------+------+---------------+------+---------+------+--------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------------+------+---------------+------+---------+------+--------+-------------+ | 1 | SIMPLE | userapplication | ALL | PRIMARY | NULL | NULL | NULL | 784422 | Using where | +----+-------------+-------------------+------+---------------+------+---------+------+--------+-------------+` </pre> <p>Any ideas how to prevent this simple query from doing a full table scan? Or am I out of luck?</p>

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