[英]SQL: How to select one record per day, assuming that each day contain more than 1 value MySQL
我想 select 記錄從'2013-04-01 00:00:00'
到'today'
但是,每一天都有很多價值,因為它們每 15 分鍾保存一個值,所以我只想要第一個或最后一個值從每一天開始。
表架構:
CREATE TABLE IF NOT EXISTS `value_magnitudes` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`value` float DEFAULT NULL,
`magnitude_id` int(11) DEFAULT NULL,
`sdi_belongs_id` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`reading_date` datetime DEFAULT NULL,
`created_at` datetime DEFAULT NULL,
`updated_at` datetime DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1118402 ;
壞 SQL:
SELECT value FROM `value_magnitudes` WHERE `value_magnitudes`.`reading_date` BETWEEN '2013-04-01 00:00:00' AND '2013-04-02 00:00:00' AND (`value_magnitudes`.magnitude_id = 234) LIMIT 1
SELECT value FROM `value_magnitudes` WHERE `value_magnitudes`.`reading_date` BETWEEN '2013-04-02 00:00:00' AND '2013-04-03 00:00:00' AND (`value_magnitudes`.magnitude_id = 234) LIMIT 1
SELECT value FROM `value_magnitudes` WHERE `value_magnitudes`.`reading_date` BETWEEN '2013-04-03 00:00:00' AND '2013-04-04 00:00:00' AND (`value_magnitudes`.magnitude_id = 234) LIMIT 1
SELECT value FROM `value_magnitudes` WHERE `value_magnitudes`.`reading_date` BETWEEN '2013-04-04 00:00:00' AND '2013-04-05 00:00:00' AND (`value_magnitudes`.magnitude_id = 234) LIMIT 1
SELECT value FROM `value_magnitudes` WHERE `value_magnitudes`.`reading_date` BETWEEN '2013-04-05 00:00:00' AND '2013-04-06 00:00:00' AND (`value_magnitudes`.magnitude_id = 234) LIMIT 1
etc ...
如果可能的話,我想合一……
十分感謝。
編輯:我的意思是,我每天都有一個查詢,但我只想從reading_date >= '2013-04-01 00:00:00'
c 進行一個查詢
EDIT2:我在該table.value_magnitudes
中有64,260條記錄,執行和響應該查詢需要很長時間,有時連接超時。
獲取您可以執行的每個日期的第一個條目
select * from value_magnitudes
where id in
(
SELECT min(id)
FROM value_magnitudes
WHERE magnitude_id = 234
and date(reading_date) >= '2013-04-01'
group by date(reading_date)
)
select * from value_magnitudes
where id in
(
SELECT min(id)
FROM value_magnitudes
WHERE `value_magnitudes`.`reading_date` BETWEEN '$from_selected' AND '$to_selected' and (magnitude_id = 234) group by date(reading_date)
)
使用上面的例子 - 如果有人需要這個 - 它正在搜索無效記錄,如果它是當天的第一行,則 action 不應為 0:
select * from log
where action=0 AND id in
(
SELECT min(id)
FROM log
group by date(ts)
)
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