PostgreSQL：Return 个基于条件和分组的条目

Question

想象一下 table：

result_id student subject grade
1         Anne    A      63
2         Anne    B      63
3         Bob     A      89
4         Bob     B      51
5         Carla   A      70
6         Carla   B      70
7         Carla   C      68
8         Dylan   B      75
9         Dylan   C      54

我想要 return 学生在科目 A 和 B 中获得完全相同成绩的条目。因此理想的输出是：

result_id student subject grade
1         Anne    A      63
2         Anne    B      63
5         Carla   A      70
6         Carla   B      70

这甚至可以通过查询来实现吗？正在努力寻找有关它的信息。

Answer 1

有点复杂，但我希望容易阅读。

select * from the_table
where student in
(
 with t as 
 (
  select student, count(*) cnt, min(grade) mig, max(grade) mag 
  from the_table 
  where subject in ('A', 'B') group by student
 )
 select student from t where mig = mag and cnt = 2
) 
and subject in ('A', 'B') 
order by student, subject;

result_id	student	subject	grade
1	Anne	A	63
2	Anne	B	63
5	Carla	A	70
6	Carla	B	70

PostgreSQL：Return 个基于条件和分组的条目

PostgreSQL: Return entries based on conditions and grouping

sql

postgresql

subquery