出5个根据关系代数写sql的题目
时间: 2024-05-15 08:13:47 浏览: 15
1. 查询学生表中的所有数据:
```
SELECT * FROM students;
```
2. 查询课程表中所有课程的名称和对应的学分:
```
SELECT course_name, credit FROM courses;
```
3. 查询选课表中选修了“计算机科学”课程的学生姓名和选课时间:
```
SELECT students.student_name, enrollment.enrollment_date
FROM students
JOIN enrollment ON students.student_id = enrollment.student_id
JOIN courses ON enrollment.course_id = courses.course_id
WHERE courses.course_name = '计算机科学';
```
4. 查询选课表中选修了3门以上课程的学生姓名和选修的课程数量:
```
SELECT students.student_name, COUNT(*) AS num_courses
FROM students
JOIN enrollment ON students.student_id = enrollment.student_id
GROUP BY students.student_name
HAVING COUNT(*) >= 3;
```
5. 查询课程表中学分最高的课程名称和学分:
```
SELECT course_name, credit
FROM courses
ORDER BY credit DESC
LIMIT 1;
```