Question

"time"                  "id",      "parameter",  "value"
"2014-02-18 18:58:00",  "1$SGP",   "A",          "415.7806091308594"
"2014-02-18 18:58:00",  "1$SGP",   "B",          "240.3373565673828"
"2014-02-18 18:58:00",  "2$SGP",   "A",          "393.191162109375"
"2014-02-18 18:58:00",  "2$SGP",   "B",          "50.10090637207031"
"2014-02-18 18:58:00",  "3$SGP",   "E",          "3484841472"
"2014-02-18 18:05:01",  "1$SGP",   "A",          "0"
"2014-02-18 17:58:01",  "1$SGP",   "B",          "0"
"2014-02-18 17:58:01",  "2$SGP",   "C",          "0"
"2014-02-18 17:58:01",  "2$SGP",   "D",          "0"
"2014-02-18 17:58:01",  "2$SGP",   "E",          "3061691904"
"2014-02-18 17:57:01",  "3$SGP",   "A",          "0"
"2014-02-18 17:57:02",  "3$SGP",   "B",          "0"

现在从Foo表中得到上述数据，我需要为所有不同的ID添加参数“A”的值，这样对于特定ID，它会从上一个时间戳中获取值。 18:00:00和19:00:00如何在考虑时间和id字段的情况下快速编写针对此要求的单个查询。

Answer 1

认为你会挣扎，因为你想要提取，但你正在索引一个日期/时间字段。

但是这样的事情应该这样做： -

SELECT SUM(value)
FROM foo
INNER JOIN
(
    SELECT id, MAX(`time`) AS maxtime
    FROM foo
    WHERE TIME(`time`) BETWEEN '18:00:00' AND '19:00:00'
    AND parameter = 'A'
    GROUP BY id
) sub1
ON foo.id = sub1.id
AND foo.`time` = sub1.maxtime

无法形成单个MySql查询以对表中的值求和

1 个答案: