SELECT COUNT(author) AS chislo_statey,
voting_count * voting_ball  / SUM(voting_count)  AS srednyaya_otsenka
FROM site_table
WHERE author='1024'
AND author_vizible='1'

+---------------+-------------------+
| chislo_statey | srednyaya_otsenka |
+---------------+-------------------+
|             12  |                  0  |
+---------------+-------------------+

CREATE TABLE `site_table` (
  `id` int( 10 ) NOT NULL auto_increment,
  `author` varchar( 5 ) NOT NULL default '1024',
  `author_vizible` enum('1','0') NOT NULL default '1',
  `voting_enabled` enum('1','0') NOT NULL default '0',
  `voting_count` varchar( 63 ) NOT NULL default '0',
  `voting_ball` varchar( 127 ) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) TYPE=MyISAM