我有几个这样的表：
const XEE是电表的计数（以kWh为单位），PO是电表的功率（以kW为单位），每15分钟从电表读取一次数据并将其写入数据库。
我正在寻找带有标记“ PO”的所有值的最大值，这就是为什么要排除所有“ EE”标记的原因。我想要返回最高值的代码，它是根据带有TAG“ PO”的时间戳
我打算使用该代码扩展具有最大，最小和AVG值及其相应时间戳的grafana仪表板（已经存在）。
这是我到目前为止的代码，但是它似乎总是选择我在WHERE子句中输入的时间范围内的第一个值：
> "dsid" "tag" "timestamp" "value"
> "989" "EE" "1445162347" "931.647"
> "990" "PO" "1445162347" "0.087"
> "991" "EE" "1445163247" "931.669"
> "992" "PO" "1445163247" "0.089"
> "993" "EE" "1445164147" "931.692"
> "994" "PO" "1445164147" "0.085"
> "995" "EE" "1445165047" "931.715"
> "996" "PO" "1445165047" "0.090"
当前我得到以下输出：
'''SELECT
FROM_UNIXTIME(timestamp) as time_sec,
'1P2' AS Meter,
tag as metric,
MIN(value) AS MIN,
MAX(VALUE) AS MAX,
AVG(VALUE) AS AVG
FROM `WSE_KA-KHW_1P2`
WHERE TAG NOT IN ('EE')
'''
我要的是这样的
"time_sec" "Meter" "metric" "MIN" "MAX" "AVG"
"2015-10-13 08:14:07" "1P2" "PO" "0.000000" "6.404" "3.2"
根据要求，下面是插入脚本代码的某些行：
"time_sec" "Meter" "metric" "MIN" "MAX" "AVG"
"2015-10-13 08:14:07" "1P2" "PO" "0.1" "" ""
"2015-12-13 10:14:07" "1P2" "PO" "" "6.404" ""
"" "1P2" "PO" "" "" "3.2"
值后的其他列不相关...
THX到@symcbean我现在已经很接近我需要实现的目标：
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (909, 'EE', 1445126346, '930.647', 1445125500, 1445126400, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (910, 'PO', 1445126346, '0.088', 1445125500, 1445126400, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (911, 'EE', 1445127246, '930.669', 1445126400, 1445127300, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (912, 'PO', 1445127246, '0.087', 1445126400, 1445127300, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (913, 'EE', 1445128146, '930.691', 1445127300, 1445128200, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (914, 'PO', 1445128146, '0.087', 1445127300, 1445128200, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (915, 'EE', 1445129046, '930.718', 1445128200, 1445129100, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (916, 'PO', 1445129046, '0.138', 1445128200, 1445129100, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (917, 'EE', 1445129947, '930.752', 1445129100, 1445130000, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (918, 'PO', 1445129947, '0.134', 1445129100, 1445130000, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (919, 'EE', 1445130847, '930.782', 1445130000, 1445130900, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (920, 'PO', 1445130847, '0.088', 1445130000, 1445130900, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (921, 'EE', 1445131747, '930.804', 1445130900, 1445131800, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (922, 'PO', 1445131747, '0.087', 1445130900, 1445131800, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (923, 'EE', 1445132647, '930.826', 1445131800, 1445132700, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (924, 'PO', 1445132647, '0.086', 1445131800, 1445132700, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (925, 'EE', 1445133547, '930.848', 1445132700, 1445133600, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (926, 'PO', 1445133547, '0.086', 1445132700, 1445133600, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (927, 'EE', 1445134447, '930.870', 1445133600, 1445134500, 0);
INSERT INTO `WSE_KA-KHW_1P2` (`dsid`, `tag`, `timestamp`, `value`, `startts`, `correctts`, `isfixed`) VALUES (928, 'PO', 1445134447, '0.087', 1445133600, 1445134500, 0);
我已经使用了grafana中的三个表，它有一个漂亮的表，但是它总是选择数据库中的第一个时间值作为时间戳。但是我需要它从1P2_MAX输出时间戳。这样我就会知道MAX到底是什么时候出现的...
当前输出如下：
SELECT records.*, aggregated.*
FROM
(
SELECT
from_unixtime(TIMESTAMP),
tag AS metric,
MAX(VALUE) AS 1P2_MAX,
AVG(VALUE) AS 1P2_AVG
FROM `WSE_KA-KHW_1P2`
WHERE TAG NOT IN ('EE')
AND from_unixtime(TIMESTAMP BETWEEN FROM_UNIXTIME(1546297200) AND FROM_UNIXTIME(1577833199))
) records JOIN
(
SELECT
tag AS metric,
MAX(VALUE) AS 1P2_MAX,
AVG(VALUE) AS 1P2_AVG
FROM `WSE_KA-KHW_1P2`
WHERE TAG NOT IN ('EE')
AND from_unixtime(TIMESTAMP BETWEEN FROM_UNIXTIME(1546297200) AND FROM_UNIXTIME(1577833199))
GROUP BY metric
) aggregated ON
records.metric=aggregated.metric
答案 0 :(得分：0)
您需要GROUP BY FROM_UNIXTIME(timestamp), tag。
（取决于DBMS的配置方式，您可能需要在分组的属性中包括文字）。
这是一个相当琐碎的SQL问题-如此之多，以至于它可以在这里键入答案而不是搜索重复项。
尽管这回答了您提出的问题-看起来您在问错了问题。尽管示例数据中的多行具有相同的标记和时间戳，但这似乎有些奇怪。我怀疑如果您真的对汇总值感兴趣，您可能想四舍五入时间值以获得更大的bin。
根据以下评论进行更新
如果您希望聚合值不与特定时间匹配。...
SELECT records.*, aggregated.*
FROM
(
SELECT *
FROM `WSE_KA-KHW_1P2`
WHERE TAG NOT IN ('EE')
AND timestamp BETWEEN _____ AND _____
) records JOIN
(
SELECT
tag AS metric,
MIN(value) AS minval,
MAX(VALUE) AS maxval,
AVG(VALUE) AS avgval
FROM `WSE_KA-KHW_1P2`
WHERE TAG NOT IN ('EE')
AND timestamp BETWEEN _____ AND _____
GROUP BY tag
) aggregated ON
records.tag=aggregated.tag
但这与您在随后的问题编辑中要求的有所不同：
我想要返回最大值的代码，并且该代码具有TAG“ PO”的时间戳
这是一个新要求。并且在样本数据中，PO为“ NOT IN（EE）”时，不一定要遵循此表达式是相符的形式。抛开这些，您似乎正在要求“逐组最大值”-您可以使用max concat trick或sub-query
来解决