SQL：Oracle avg over group

Question

我想在示例中展示我的问题。 所以，我有学生，他们在不同的学校学习，我想按学校计算平均数，然后计算总平均数。

示例：

那么，我怎么能得到像这样的结果？

提前致谢！

还有一个选择 - 在一个查询中执行此操作会非常舒服。

Answer 1

with
     marks ( school, student, mark ) as (
       select 'School 1', 'James' , 5 from dual union all
       select 'School 1', 'Mark'  , 4 from dual union all
       select 'School 1', 'Howard', 5 from dual union all
       select 'School 4', 'Jho'   , 4 from dual union all
       select 'School 5', 'Kate'  , 5 from dual
     ),
     a ( school, s_avg ) as (
       select   school, avg(mark) 
       from     marks
       group by school
     )
select school, student, mark,
       avg(mark) over (partition by school) as avg_by_school,
       (select avg(s_avg) from a) as global_avg
from   marks;


SCHOOL   STUDENT       MARK AVG_BY_SCHOOL GLOBAL_AVG
-------- ------- ---------- ------------- ----------
School 1 James            5         4.667      4.556
School 1 Mark             4         4.667      4.556
School 1 Howard           5         4.667      4.556
School 4 Jho              4         4.000      4.556
School 5 Kate             5         5.000      4.556

5 rows selected.