oracle 查询子查询返回和父查询对应

Question

select  staff_id  ,sum(grade_id)/(select count(*) from tb_order_history group by staff_id )
        
        from tb_order_history ,tb_feedback
        
        where tb_order_history.feedback_id = tb_feedback.feedback_id group by tb_order_history.staff_id

``` 
 现在因为子查询返回多行，所以报错。我想除数位置的子查询按staff_id 分组 统计返回的count（*）和父查询的staff_id 对应，该怎么办，求大神解答，多谢！！
```

Answer 1

创建子查询为视图，关联tb_order_history和视图，以staff_id ，sum(grade)为分组依据