Just like this: common.Select().from('table1') .from('table2', 'id2', 'table1', 'id1', 'LEFT').fun('AVG', 'col').build(); "SELECT AVG(`t2`.`col`) FROM `table1` `t1` LEFT JOIN `table2` `t2` ON `t2`.`id2` = `t1`.`id1`" thanks