add : 596

h-j-13 · h-j-13 · commit e43348ef2235 · 2017-12-11T16:05:26.000+08:00
diff --git a/Soulution/LeetCode 596. Classes More Than 5 Students.md b/Soulution/LeetCode 596. Classes More Than 5 Students.md
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+# LeetCode 596. Classes More Than 5 Students
+## 题目
+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.
+
+题目大意,找出选修人数超过5门的学生,每门课的学生不应该重复计算
+
+## 解题思路
+
+使用 group by 分组后 count(distinct 学生) 大于5的即为需要展示的内容
+
+```sql
+SELECT class FROM courses GROUP BY class  HAVING count(DISTINCT student) >= 5;
+```
