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Leetcode596 Classes More Than 5 Students

Posted on Edited on In Valine:

Problem:

Intuition:

对 class 列进行分组之后，再使用 count 汇总函数统计每个分组的记录个数，之后使用 HAVING 进行筛选。HAVING 针对分组进行筛选，而 WHERE 针对每个记录（行）进行筛选。
我们需要注意涉及到统计（SUM,COUNT）之类的操作一般都用group by 来进行处理。

Solution:

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SELECT
    class
FROM
    courses
GROUP BY
    class
HAVING
    count( DISTINCT student ) >= 5;