$data=$model->where(array(
'serial_number'=>array(array('eq', ''), array('exp', 'is null'), 'or'),
'train' =>array(array('eq', ''), array('exp', 'is null'), 'or'),
'stu_status' =>array('in', '23,3'),
))->select();
要生成这样sql如何修改
select * from zm_student where (serial_number='' or train='') and stu_status in (23,3)