聚合操作

count

$this->db()->table('user')->count('id');

max

$this->db()->table('user')->max('id');

min

$this->db()->table('user')->min('id');

sum

$this->db()->table('user')->sum('id');

avg

$this->db()->table('user')->avg('id');

原文: http://doc.cmlphp.com/devintro/model/mysql/aggregation.html