2020/11/13 刘一辰的JAVA随笔

今日目标：Mysql学习17

实验内容：

-- 11.查询每门课的平均成绩

SELECT c_no,AVG(sc_degree) FROM SCORE GROUP BY c_no;

+-------+----------------+

| c_no  | AVG(sc_degree) |

+-------+----------------+

| 3-105 |        87.6667 |

| 3-245 |        76.3333 |

| 6-166 |        81.6667 |

+-------+----------------+

 

 

 

-- 12,查询score表中至少有2名学生选修的,并且以3开头的课程的平均分

SELECT AVG(sc_degree),c_no  from score GROUP BY c_no HAVING COUNT(c_no)  >= 2 AND c_no like '3%'  ;

+----------------+-------+

| AVG(sc_degree) | c_no  |

+----------------+-------+

|        85.3333 | 3-105 |

|        76.3333 | 3-245 |

+----------------+-------+