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  • 【leetcode database】Human Traffic of Stadium

    X city built a new stadium, each day many people visit it and the stats are saved as these columns: id, date, people
    
    Please write a query to display the records which have 3 or more consecutive rows and the amount of people more than 100(inclusive).
    
    For example, the table stadium:
    +------+------------+-----------+
    | id   | 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       |
    +------+------------+-----------+
    For the sample data above, the output is:
    
    +------+------------+-----------+
    | id   | date       | people    |
    +------+------------+-----------+
    | 5    | 2017-01-05 | 145       |
    | 6    | 2017-01-06 | 1455      |
    | 7    | 2017-01-07 | 199       |
    | 8    | 2017-01-08 | 188       |
    +------+------------+-----------+
    Note:
    Each day only have one row record, and the dates are increasing with id increasing.

    这题的难度属于hard级别,但我觉得最多也就是一般难度。初看起来这题好像有点不知所措,但仔细分析却能发现其实条件很简单,只要满足以下任意三个条件即可:

    1.id in (x,x+1,x+2) 的记录的people >= 100;

    2.1.id in (x,x+1,x-1) 的记录的people >= 100;

    3.1.id in (x,x-1,x-2) 的记录的people >= 100;

    代码如下:

    select * from stadium a   where a.people >= 100 and 
    (
    (
    a.id+1 in  (select id from stadium where people >= 100) 
    and 
    a.id+2 in  (select id from stadium where people >= 100) 
    )
    or 
    (
    a.id-1  in  (select id from stadium where people >= 100) 
    and 
    a.id+1  in  (select id from stadium where people >= 100) 
    )
    or 
    (
    a.id-1  in  (select id from stadium where people >= 100) 
    and 
    a.id-2  in  (select id from stadium where people >= 100) 
    )
    );
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  • 原文地址:https://www.cnblogs.com/seyjs/p/7081517.html
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