★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★
➤微信公众号：山青咏芝（shanqingyongzhi）➤博客园地址：山青咏芝（）➤GitHub地址：➤原文地址： ➤如果链接不是山青咏芝的博客园地址，则可能是爬取作者的文章。➤原文已修改更新！强烈建议点击原文地址阅读！支持作者！支持原创！★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★1 Create table If Not Exists courses (student varchar(255), class varchar(255)) 2 Truncate table courses 3 insert into courses (student, class) values ('A', 'Math') 4 insert into courses (student, class) values ('B', 'English') 5 insert into courses (student, class) values ('C', 'Math') 6 insert into courses (student, class) values ('D', 'Biology') 7 insert into courses (student, class) values ('E', 'Math') 8 insert into courses (student, class) values ('F', 'Computer') 9 insert into courses (student, class) values ('G', 'Math')10 insert into courses (student, class) values ('H', 'Math')11 insert into courses (student, class) values ('I', 'Math') There is a table courses with columns: student and class
Please list out all classes which have more than or equal to 5 students.
For example, the table:
+---------+------------+| student | class |+---------+------------+| A | Math || B | English || C | Math || D | Biology || E | Math || F | Computer || G | Math || H | Math || I | Math |+---------+------------+
Should output:
+---------+| class |+---------+| Math |+---------+
Note:
The students should not be counted duplicate in each course.有一个courses 表 ，有: student (学生) 和 class (课程)。
请列出所有超过或等于5名学生的课。
例如,表:
+---------+------------+| student | class |+---------+------------+| A | Math || B | English || C | Math || D | Biology || E | Math || F | Computer || G | Math || H | Math || I | Math |+---------+------------+
应该输出:
+---------+| class |+---------+| Math |+---------+
Note:
学生在每个课中不应被重复计算。1465ms
1 # Write your MySQL query statement below2 select class3 from courses group by class having COUNT(DISTINCT student) >= 5
1479ms
1 # Write your MySQL query statement below2 SELECT 3 class4 FROM5 courses6 GROUP BY class7 HAVING COUNT(DISTINCT student)>=5