判断字段null
~~~
$map['id'] = array('exp',' is NULL');
SELECT * FROM `gws_peoples` WHERE (`resident_no` IS NOT NULL) AND (`paper_no` IS NOT NULL);
~~~
~~~
SELECT * FROM `gws_peoples` WHERE (`resident_no` IS NOT NULL) AND (`paper_no` IS NOT NULL) AND (TRIM(`resident_no`)<>'') AND (TRIM(`paper_no`)<>'');
~~~