将连接查询转换为嵌套查询
convert join query into nested query
如何将此查询转换为使用 where in 条件的嵌套查询？
SELECT schedule.subcode,attendance.usn,avg(attendance.ispresent)*100 as Attendance_Percentage
FROM schedule JOIN attendance ON schedule.sched_id=attendance.sched_id
WHERE usn="4jc14is013" AND subcode="is530";
您可以使用 HAVING:
SELECT usn, name, AVG(ispresent) attendance FROM table
GROUP BY usn, name HAVING attendance < 0.75;
如何将此查询转换为使用 where in 条件的嵌套查询？
SELECT schedule.subcode,attendance.usn,avg(attendance.ispresent)*100 as Attendance_Percentage FROM schedule JOIN attendance ON schedule.sched_id=attendance.sched_id WHERE usn="4jc14is013" AND subcode="is530";
您可以使用 HAVING:
SELECT usn, name, AVG(ispresent) attendance FROM table
GROUP BY usn, name HAVING attendance < 0.75;