显示作为活动主管的职责最多的户外教练的姓名

Question

架构是：
 ACTIVITY_SUPERVISOR（SupervisorID）
 OUTDOOR_INSTRUCTOR（InstructorID，InstrName，InstrPhone，SupervisorID）

这是我写的，但它不起作用

 SELECT O.InstructorID, O.InstrName, O.SupervisorID, A.SupervisorID, COUNT(*) 
 FROM Outdoor_instructor O, Activity_supervisor A 
 INNER JOIN Activity_supervisor A ON A.SupervisorID = O.SupervisorID 
 GROUP BY SupervisorID O, InstrName O 
 ORDER BY COUNT(*) DESC 
 LIMIT 1; 

Answer 1

您的查询中有两个对“Activity_supervisor A”的引用。 您的分组中还应包含更多值

试试这个：

 SELECT O.InstructorID, O.InstrName, O.SupervisorID, A.SupervisorID, COUNT(*) 
 FROM Outdoor_instructor O
 INNER JOIN Activity_supervisor A ON A.SupervisorID = O.SupervisorID 
 WHERE rownum = 1
 GROUP BY O.InstructorID, O.InstrName, O.SupervisorID, A.SupervisorID 
 ORDER BY COUNT(*) DESC