CREATE TABLE users (
  name char( 20 ),
  user_count char( 20 ),
  id int( 10 ) unsigned NOT NULL auto_increment,
  description text NOT NULL,
  PRIMARY KEY  (id)
) TYPE=MyISAM;

CREATE TABLE arrival (
  id int( 11 ) NOT NULL auto_increment,
  userid int( 11 ) NOT NULL default '0',
  summa double( 10 , 2 ) NOT NULL default '0.00',
  description char( 255 ) NOT NULL default '',
  data datetime NOT NULL default '0000-00-00 00:00:00',
  PRIMARY KEY  (id),
  KEY userid (userid)
) TYPE=MyISAM;

CREATE TABLE pay (
  id int( 11 ) NOT NULL auto_increment,
  userid int( 11 ) NOT NULL default '0',
  summa double( 10 , 2 ) NOT NULL default '0.00',
  description char( 255 ) NOT NULL default '',
  PRIMARY KEY  (id),
  KEY userid (userid)
) TYPE=MyISAM;

select 
   users.id,
   users.name,
   sum(arrival.summa)/count(arrival.userid)/count(distinct arrival.userid) as 'summa_in',
   sum(pay.summa)/count(pay.userid)/count(distinct pay.userid) as 'summa_out' from users 
  left join arrival on arrival.userid=users.id 
  left join pay on pay.userid=users.id 
group by users.id 
order by users.name