对于每个学生，找到他们选择的课程数量并进行排序 行按降序排列。 （例如学生ID，数量 该学生参加的课程）
STUDENT TABLE
| ID | name | dept_name | tot_cred |
| S0901 | Alice | Comp.Sci. | 83 |
| S0902 | Martha | Comp.Sci. | 75 |
| S0903 | Micheal | Comp.Sci. | 45 |
| S0904 | Rose | Comp.Sci. | 77 |
| S0905 | Alfie | Comp.Sci. | 91 |
| S1901 | Brad | Biology | 23 |
TAKES TABLE
| ID | course_id | sec_id | semester | year | grade
| S0901 | CS-101 | 1 | Fall | 2009 | A
| S0901 | CS-315 | 1 | Spring | 2010 | B+
| S0901 | HIS-351 | 1 | Spring | 2010 | A-
| S0901 | MTH-101 | 1 | Fall | 2009 | A
| S0901 | MTH-102 | 1 | Spring | 2009 | B+
| S0902 | CS-101 | 1 | Fall | 2009 | A
| S0902 | CS-315 | 1 | Spring | 2010 | B+
| S0902 | CS-319 | 1 | Spring | 2010 | B
| S0902 | HIS-351 | 1 | Spring | 2010 | A-
| S0902 | MTH-101 | 1 | Fall | 2009 | A
| S0902 | MTH-102 | 1 | Spring | 2009 | B+
| S1901 | CS-101 | 1 | Fall | 2009 | B+
| S1901 | CS-190 | 1 | Spring | 2009 | C
| S1901 | CS-315 | 1 | Spring | 2010 | A-
| S1901 | HIS-351 | 1 | Spring | 2010 | A-
答案 0 :(得分：1)
从技术上讲，@ Marcinek的答案可能不够，因为它省略了零课程的学生。我会改用它：
SELECT STUDENT.ID, COUNT(TAKES.ID)
FROM STUDENT LEFT JOIN TAKES ON STUDENT.ID = TAKES.ID
GROUP BY STUDENT.ID
ORDER BY COUNT(TAKES.ID) DESC;
通过使用LEFT JOIN，您可以捕获ID未出现在TAKES表中的学生。
答案 1 :(得分：0)
只需加入并对结果进行分组。
SELECT COUNT(*), s.id FROM student s, takes t where t.id = s.id group by s.id order by count(*) desc