文章目錄

• • 1. 題目
  • 2. 解題

1. 題目

X 市建了一個新的體育館，每日人流量信息被記錄在這三列信息中：序號 (id)、日期 (visit_date)、 人流量 (people)。

請編寫一個查詢語句，找出人流量的高峰期。高峰期時，至少連續三行記錄中的人流量不少于100。

例如，表 stadium：

+------+------------+-----------+ | id | visit_date | people | +------+------------+-----------+ | 1 | 2017-01-01 | 10 | | 2 | 2017-01-02 | 109 | | 3 | 2017-01-03 | 150 | | 4 | 2017-01-04 | 99 | | 5 | 2017-01-05 | 145 | | 6 | 2017-01-06 | 1455 | | 7 | 2017-01-07 | 199 | | 8 | 2017-01-08 | 188 | +------+------------+-----------+

對于上面的示例數據，輸出為：

+------+------------+-----------+ | id | visit_date | people | +------+------------+-----------+ | 5 | 2017-01-05 | 145 | | 6 | 2017-01-06 | 1455 | | 7 | 2017-01-07 | 199 | | 8 | 2017-01-08 | 188 | +------+------------+-----------+

提示：
每天只有一行記錄，日期隨著 id 的增加而增加。

來源：力扣（LeetCode）
鏈接：https://leetcode-cn.com/problems/human-traffic-of-stadium
著作權歸領扣網絡所有。商業轉載請聯系官方授權，非商業轉載請注明出處。

2. 解題

• 使用 id 跟排序行號做差，連續的做差是一樣的

select stadium.*, id - cast(row_number() over(partition by people >= 100) as signed) rnk from stadium where people >= 100 {"headers": ["id", "visit_date", "people", "rnk"], "values": [ [2, "2017-01-02", 109, 1], [3, "2017-01-03", 150, 1], [5, "2017-01-05", 145, 2], [6, "2017-01-06", 1455, 2], [7, "2017-01-07", 199, 2], [8, "2017-01-08", 188, 2]]}

• 再套一層，算出 rnk 一樣的有多少個

select id, visit_date, people,count(*) over(partition by rnk) cntfrom (select stadium.*, id - cast(row_number() over(partition by people >= 100) as signed) rnkfrom stadiumwhere people >= 100 ) t {"headers": ["id", "visit_date", "people", "cnt"], "values": [ [2, "2017-01-02", 109, 2], [3, "2017-01-03", 150, 2], [5, "2017-01-05", 145, 4], [6, "2017-01-06", 1455, 4], [7, "2017-01-07", 199, 4], [8, "2017-01-08", 188, 4]]}

• 最后篩選 cnt >= 3 的

# Write your MySQL query statement below select id, visit_date, people from (select id, visit_date, people,count(*) over(partition by rnk) cntfrom(select stadium.*, id - cast(row_number() over(partition by people >= 100) as signed) rnkfrom stadiumwhere people >= 100) t ) t where cnt >= 3

或者 3表連接

# Write your MySQL query statement below select distinct a.* from stadium a, stadium b, stadium c where ((b.id = a.id+1 and c.id = b.id+1) or(c.id = b.id+1 and a.id = c.id+1) or(a.id = c.id+1 and b.id = a.id+1))and a.people>=100 and b.people>=100 and c.people>=100 order by a.id

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