谁帮忙写三个sql语句

[zxle]

四个表：
1学生表(学号 姓名 省份)
2系表(系ID 系名 学号)
3课程表（课程ID 名称 学生)
4成绩表(学号 课程ID 成绩)

要求写三个sql查询语句：
1 列出选修课程最多学生
2 列出选修“计算机原理”学生最少的系
3 列出每个系成绩的及格率（系的学生所选课程及格数/总课程数）

[fmfsaisai]

我怎么感觉这个应该放在Bitcoin节点

[listenEcho]

1. To find the student who has taken the most courses:



SELECT student, COUNT(*) as num_courses
FROM courses
GROUP BY student
ORDER BY num_courses DESC
LIMIT 1;


2. To find the department with the least number of students taking the course "Computer Principles":

SELECT department, COUNT(*) as num_students
FROM students
JOIN departments ON students.student_id = departments.student_id
JOIN courses ON students.student_id = courses.student_id
WHERE courses.name = 'Computer Principles'
GROUP BY department
ORDER BY num_students ASC
LIMIT 1;


3. To find the pass rate for each department (the percentage of courses passed by students in the department):

SELECT department,
SUM(CASE WHEN grades.grade >= 60 THEN 1 ELSE 0 END) / COUNT(*) AS pass_rate
FROM students
JOIN departments ON students.student_id = departments.student_id
JOIN grades ON students.student_id = grades.student_id
GROUP BY department;


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