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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 below 2 select class 3 from courses group by class having COUNT(DISTINCT student) >= 5
1479ms
1 # Write your MySQL query statement below 2 SELECT 3 class 4 FROM 5 courses 6 GROUP BY class 7 HAVING COUNT(DISTINCT student)>=5