class get_c_str { var $str; var $start_str; var $end_str; var $start_pos; var $end_pos; var $c_str_l; var $contents; function get_str($str,$start_str,$end_str){ $this->str = $str; $this->start_str = $start_str; $this->end_str = $end_str; $this-&g
假设有两个表A,B,都只有一个字段PHONE 1,MINUS SELECT PHONE FROM A MINUS SELECT PHONE FROM B; 相当于用结果集A减去结果B得出的结果集.同样的效果也可以用SELECT PHONE FROM A WHERE NOT EXISTS(SELECT 1 FROM B WHERE A.PHOEN=B.PHONE)来达到. 2,INTERSECT SELECT PHONE FROM A INTERSECT SELECT PHONE FROM