mysql条件查询-排除null ---oracle、mysql 区分总结
SELECT c.`COURSE_NO` FROM sub_course c WHERE c.`CLASS_INFO`='999' AND IFNULL(c.`COURSE_NO`,'-1') != '-1' ;
SELECT c.`COURSE_NO` FROM sub_course c WHERE c.`CLASS_INFO`='999' AND IFNULL(c.`COURSE_NO`,'-1') != '-1' ;