Question

所以，我在MySQL表中得到了以下数据：

mysql> SELECT * FROM reading LIMIT 0,10;
+----+---------------------+-------+-------------+
| id | date                | power | temperature |
+----+---------------------+-------+-------------+
|  1 | 2011-02-15 21:58:41 |   124 |          22 |
|  2 | 2011-02-15 21:58:47 |   123 |          22 |
|  3 | 2011-02-15 21:58:53 |   124 |          22 |
|  4 | 2011-02-15 21:58:59 |   686 |          22 |
|  5 | 2011-02-15 21:59:05 |   126 |          22 |
|  6 | 2011-02-15 21:59:11 |   123 |          22 |
|  7 | 2011-02-15 21:59:17 |   122 |          22 |
|  8 | 2011-02-15 21:59:47 |   122 |          22 |
|  9 | 2011-02-15 21:59:59 |   122 |          22 |
| 10 | 2011-02-15 22:00:29 |   123 |          22 |
+----+---------------------+-------+-------------+
10 rows in set (0.00 sec)

（这些是来自当前成本设备的读数并不是秘密）

现在，我一直在争夺SQL几个小时，以便在15分钟内获得平均功率。我能得到的最接近的是：

SELECT
    CONCAT( 
        DATE(date), ' ',
        HOUR(date), ':',
        CASE
            WHEN MINUTE(date) BETWEEN  0 AND 14 THEN '00'
            WHEN MINUTE(date) BETWEEN 15 AND 29 THEN '15'
            WHEN MINUTE(date) BETWEEN 30 AND 44 THEN '30'
            WHEN MINUTE(date) BETWEEN 45 AND 59 THEN '45'
        END
    ) AS date,
    ROUND(AVG(power),1)
FROM reading
WHERE date > '2011-02-20' AND date < '2011-02-21'
GROUP BY date;

这给我的结果如下：

mysql> SELECT
    ->     CONCAT( 
    ->         DATE(date), ' ',
    ->         HOUR(date), ':',
    ->         CASE
    ->             WHEN MINUTE(date) BETWEEN  0 AND 14 THEN '00'
    ->             WHEN MINUTE(date) BETWEEN 15 AND 29 THEN '15'
    ->             WHEN MINUTE(date) BETWEEN 30 AND 44 THEN '30'
    ->             WHEN MINUTE(date) BETWEEN 45 AND 59 THEN '45'
    ->         END
    ->     ) AS date,
    -> ROUND(AVG(power),1)
    -> FROM reading
    -> WHERE date > '2011-02-20' AND date < '2011-02-21'
    -> GROUP BY date LIMIT 0,10;
+-----------------+---------------------+
| date            | ROUND(AVG(power),1) |
+-----------------+---------------------+
| 2011-02-20 0:00 |               320.0 |
| 2011-02-20 0:00 |               319.0 |
| 2011-02-20 0:00 |               317.0 |
| 2011-02-20 0:00 |               313.0 |
| 2011-02-20 0:00 |               315.0 |
| 2011-02-20 0:00 |               315.0 |
| 2011-02-20 0:00 |               320.0 |
| 2011-02-20 0:00 |               315.0 |
| 2011-02-20 0:00 |               315.0 |
| 2011-02-20 0:00 |               313.0 |
[...]
| 2011-02-20 0:45 |               316.0 |
| 2011-02-20 0:45 |               311.0 |
| 2011-02-20 0:45 |               310.0 |
| 2011-02-20 0:45 |               317.0 |
| 2011-02-20 0:45 |               311.0 |
| 2011-02-20 0:45 |               312.0 |
| 2011-02-20 0:45 |               318.0 |
| 2011-02-20 0:45 |               315.0 |
| 2011-02-20 0:45 |               313.0 |
| 2011-02-20 0:45 |               316.0 |
| 2011-02-20 0:45 |               311.0 |
| 2011-02-20 0:45 |               312.0 |
| 2011-02-20 0:45 |               319.0 |
| 2011-02-20 0:45 |               312.0 |
[...]
| 2011-02-20 4:00 |                95.0 |
| 2011-02-20 4:15 |                95.0 |
| 2011-02-20 4:15 |                95.0 |
| 2011-02-20 4:15 |                94.0 |
| 2011-02-20 4:15 |                94.0 |
| 2011-02-20 4:15 |                94.0 |
| 2011-02-20 4:15 |                94.0 |
| 2011-02-20 4:15 |                94.0 |
| 2011-02-20 4:15 |                94.0 |
| 2011-02-20 4:15 |                96.0 |
| 2011-02-20 4:15 |                93.0 |
| 2011-02-20 4:15 |                94.0 |
| 2011-02-20 4:15 |                93.0 |
| 2011-02-20 4:15 |                93.0 |
+-----------------+---------------------+
10 rows in set, 1 warning (0.20 sec)

这与我想要的东西相差甚远。看起来我非常接近我需要的东西，只需要DISTINCT日期字段并获取所有相等日期字段的平均值，但我无法获得正确的SQL。

我的目标结果是：

| 2011-02-20 4:00 |                94.0 |
| 2011-02-20 4:15 |               194.3 |
| 2011-02-20 4:30 |               197.4 |
| 2011-02-20 4:45 |               145.3 |
| 2011-02-20 5:00 |                94.0 |
| 2011-02-20 5:15 |                96.0 |
| 2011-02-20 5:30 |                93.0 |
| 2011-02-20 5:45 |                94.0 |

非常感谢任何帮助或提示。

Answer 1

MySQL变得混乱，因为您将CONCAT()输出别名与现有列的名称相同，因此GROUP BY date按表的日期字段进行分组，而不是你的四舍五入到最近的15分钟日期。

您需要将查询更改为

mysql> SELECT
    ->     CONCAT( 
    ->         DATE(date), ' ',
    ->         HOUR(date), ':',
    ->         CASE
    ->             WHEN MINUTE(date) BETWEEN  0 AND 14 THEN '00'
    ->             WHEN MINUTE(date) BETWEEN 15 AND 29 THEN '15'
    ->             WHEN MINUTE(date) BETWEEN 30 AND 44 THEN '30'
    ->             WHEN MINUTE(date) BETWEEN 45 AND 59 THEN '45'
    ->         END
    ->     ) AS quarterhour,
    -> ROUND(AVG(power),1)
    -> FROM reading
    -> WHERE date > '2011-02-20' AND date < '2011-02-21'
    -> GROUP BY quarterhour LIMIT 0,10;

此外，我会使用HOUR()来代替DATE_FORMAT()而不是小时，否则“5”（5 AM）会在“17”（5 PM）之后出现。

CONCAT(DATE_FORMAT(date,'%Y-%m-%d %H:'), CASE ... END)应该完成这项工作。

通过DISTINCT，CONCATenate日期列与AVERAGE进行MySQL SQL查询

1 个答案: