我想从'2013-04-01 00:00:00'
到'today'
选择记录但是,每天都有很多价值,因为他们每15分钟保存一个值,所以我只想要每个值的第一个或最后一个值一天。
表架构:
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 ;
错误的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 ...
如果可能的话,我想要一个人......
非常感谢你。
修改
我的意思是,我每天都有一个查询,但我只是想从reading_date >= '2013-04-01 00:00:00'
c进行一次查询
EDIT2:
我在那个table.value_magnitudes
中有 64,260 个记录,并且需要太长时间才能执行和响应该查询,有时还需要超时连接。
答案 0 :(得分:5)
获取您可以执行的每个日期的第一个条目
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)
)
答案 1 :(得分:2)
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)
)