_601.sql

-- 601. 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.

SELECT s1.* FROM stadium AS s1, stadium AS s2, stadium as s3
    WHERE
    ((s1.id + 1 = s2.id
    AND s1.id + 2 = s3.id)
    OR
    (s1.id - 1 = s2.id
    AND s1.id + 1 = s3.id)
    OR
    (s1.id - 2 = s2.id
    AND s1.id - 1 = s3.id)
    )
    AND s1.people>=100
    AND s2.people>=100
    AND s3.people>=100

    GROUP BY s1.id