将联接查询转换为嵌套查询

Question

如何将此查询转换为使用where in condition的嵌套查询?

SELECT schedule.subcode,attendance.usn,avg(attendance.ispresent)*100作为Attendance_Percentageschedule.sched_id=attend .sched_idWHERE 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;