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  • [SQL]LeetCode596. 超过5名学生的课 | Classes More Than 5 Students

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    SQL架构

     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
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  • 原文地址:https://www.cnblogs.com/strengthen/p/10450346.html
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