sql练习题及经典题

https://blog.csdn.net/mrbcy/article/details/68965271

经典例题

19.查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。

SELECT s1.Sno,s1.Degree
FROM Scores AS s1 INNER JOIN Scores AS s2
ON(s1.Cno=s2.Cno AND s1.Degree>s2.Degree)
WHERE s1.Cno='3-105' AND s2.Sno='109'
ORDER BY s1.Sno;

12.查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。

SELECT Cno,AVG(Degree)
FROM Scores
WHERE Cno LIKE '3%'
GROUP BY Cno
HAVING COUNT(Sno) >= 5;

10.查询Score表中的最高分的学生学号和课程号。

SELECT Sno,Cno
FROM Scores
ORDER BY Degree DESC
LIMIT 1;