Question

如果我有一个如下表，我该如何计数和汇总所有不同的值？

student_name | section | score | class
-------------|---------|-------|-------
John         | B       | 32    | 8
Doe          | B       | 43    | 8
Jane         | A       | 33    | 8
Smith        | A       | 88    | 8
Pat          | B       | 99    | 9

每个班级我都希望得到以下输出。因此，对于类8，它将是：

section  |  num_records | score_total
---------|--------------|-------------
B        |   2          | 75
A        |   2          | 121
Total    |   4          | 196

Answer 1

您可以使用GROUPING SETS：

SELECT COALESCE(section, 'Total') AS section,
       COUNT(*) AS num_records,
       SUM(score) AS score_total
FROM t
WHERE class = 8
GROUP BY GROUPING SETS (section, ())
ORDER BY section;

db<>fiddle demo

Answer 2

您可以使用全部合并和子查询

select section,count(*),sum(score)
from t
where class =8
group by section
union all
select 'Total',count(*),sum(score) from t
where class=8

demo 输出

section     count   sum
 A           2      121
 B           2      75
Total        4      196

如何计算所有不同的行？

2 个答案: