关于校本选课查询结果的mysql代码记录

数据库中代码如下

SELECT
* 
FROM
(
SELECT
* 
FROM
users tb1 
WHERE
( SELECT count( 1 ) AS num FROM timetable tb2 WHERE tb1.uid = tb2.timetable_uid AND LEFT(tb2.timetable_cid,2) = '10' ) = 0 
) t 
WHERE
LEFT ( t.uid, 4 )= '2023'

其中：最后='2023'代表年级，中间='10'代表类别如文化素养，='20'代表体育运动。