Join 每个类别的Mysql连接和计数

嗨，我有一张这样的桌子
考试

id | exam_name
1  | computer science
2  | Environment science

id | exam_id | student_name
1  | 1       | Josh
2  | 1       | Michael
3  | 1       | John

考试学生

id | exam_name
1  | computer science
2  | Environment science

id | exam_id | student_name
1  | 1       | Josh
2  | 1       | Michael
3  | 1       | John

我只需要加入并计算每次考试的学生总数，然后输出如下内容

exam_name          | total_students |
computer science   | 3              |
Environment science| 0              |

感谢您的帮助和建议

试试这个

SELECT
    a.exam_name, count(b.id) AS total_students
FROM
    exams a
LEFT JOIN exam_students b ON a.id = b.exam_id
GROUP BY
    a.id

希望这有帮助

不，它只会给“计算机科学”一个答案，它会忽略环境科学