如何从 table 获取小时内的第一行和最后一行

Question

我正在尝试创建一个图表来显示一天内每小时的耗电量。我的设备每 15 分钟向我的服务器发送一次数据，之前的 power_kwh 总是等于或大于 sensor_id 内的 power_kwh 的当前值。在某些情况下，一栋建筑物可能有两个或更多功率计，因此我需要考虑将具有相同 periods.So 的值组合在一起我想每小时检索两行，其中第一个值和最后一个值包含 sensor_id 值所以我有 table 具有值：日期，power_kwh，sensor_id mytable

在互联网上搜索了一段时间后，我发现查询很好，但 sensor_id

有问题

SELECT
    DATE,
    power_kwh,
    sensor_id
FROM
    sensor_data
WHERE
    (HOUR(DATE), MINUTE(DATE)) IN(
        SELECT
            HOUR(DATE),
            MIN(MINUTE(DATE))
        FROM
            sensor_data
        GROUP BY
            HOUR(DATE)
    )
UNION
SELECT
    DATE,
    power_kwh,
    sensor_id
FROM
    sensor_data
WHERE
    (HOUR(DATE), MINUTE(DATE)) IN(
        SELECT
            HOUR(DATE),
            MAX(MINUTE(DATE))
        FROM
            sensor_data
        GROUP BY
            HOUR(DATE)
    );

My current result
+----------------------------+-----------+-----------+
| date                       | power_kwh | sensor_id |
+----------------------------+-----------+-----------+
| 2020-03-12 15:40:03.000000 | 682685.56 |         4 |
| 2020-03-12 15:59:03.000000 | 682688.44 |         5 |
| 2020-03-12 16:00:03.000000 | 682688.56 |         5 |
| 2020-03-12 16:59:06.000000 | 682697.44 |         5 |
| 2020-03-12 17:00:06.000000 | 682697.56 |         5 |
| 2020-03-12 17:59:08.000000 | 682706.44 |         5 |
| 2020-03-12 18:00:08.000000 | 682706.56 |         5 |
| 2020-03-12 18:59:11.000000 | 682715.44 |         5 |
| 2020-03-12 19:00:11.000000 | 682715.56 |         5 |
| 2020-03-12 19:59:13.000000 | 682724.44 |         5 |
| 2020-03-12 20:00:13.000000 | 682724.56 |         5 |
| 2020-03-12 20:59:16.000000 | 682733.44 |         5 |



My expected result
+----------------------------+-----------+-----------+
| date                       | power_kwh | sensor_id |
+----------------------------+-----------+-----------+
| 2020-03-12 15:40:03.000000 | 153566.34 |         4 |
| 2020-03-12 15:59:03.000000 | 153575.44 |         4 |
| 2020-03-12 15:00:02.000000 | 682688.56 |         5 |
| 2020-03-12 15:58:06.000000 | 682697.44 |         5 |
| 2020-03-12 16:00:06.000000 | 153576.23 |         4 |
| 2020-03-12 16:59:08.000000 | 153585.44 |         4 |
| 2020-03-12 16:02:08.000000 | 682706.56 |         5 |
| 2020-03-12 16:59:11.000000 | 682715.44 |         5 |

我的 sql 版本是

mysql  Ver 8.0.19 for osx10.14 on x86_64 (Homebrew)

还有一件事，我在考虑速度和其他问题，所以如果没有解决方案，你能给我建议在 Java Spring 中处理它吗让我知道你们是否需要更多信息。谢谢！！！

Answer 1

如果你是运行MySQL8.0，可以使用window功能：

select date, power_kwh, sensor_id
from (
    select 
        s.*,
        row_number() over(partition by s.sensor_id, date(s.date), hour(s.date) order by s.date) rn_asc,
        row_number() over(partition by s.sensor_id, date(s.date), hour(s.date) order by s.date desc) rn_desc
    from sensor_data s
) t
where rn_asc = 1 or rn_desc = 1

在早期版本中，您可以使用聚合查询进行连接：

select s.date, s.power_kwh, s.sensor_id
from sensor_data s
inner join (
    select sensor_id, min(date) min_date, max(date) max_date
    from sensor_data
    group by sensor_id, date(date), hour(date)
) g
    on g.sensor_id = s.sensor_id
    and s.date in (g.min_date, g.max_date)

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