mysql - 将连接查询转换为嵌套查询

Question

如何将此查询转换为使用 where in 条件的嵌套查询？

选择 schedule.subcode,attendance.usn,avg(attendance.ispresent)*100 as Attendance_Percentage FROM schedule 加入出勤时间 schedule.sched_id=attendance.sched_id WHERE usn="4jc14is013" AND subcode="is530";

Answer 1

您可以使用HAVING：

SELECT usn, name, AVG(ispresent) attendance FROM table 
GROUP BY usn, name HAVING attendance < 0.75;