希望得到一些关于这个查询的帮助,我已经在它上面工作了一段时间,并且无法更快地得到它:
SELECT date, count(id) as 'visits' FROM dates
LEFT OUTER JOIN visits
ON (dates.date = DATE(visits.start) and account_id = 40 )
WHERE date >= '2010-12-13' AND date <= '2011-1-13'
GROUP BY date ORDER BY date ASC
该查询大约需要8秒才能运行。我在dates.date,visits.start,visits.account_id和visits.start + visits.account_id上添加了索引,无法让它更快地运行。
表结构(仅显示访问表中的相关列):
create table visits (
`id` int(11) NOT NULL AUTO_INCREMENT,
`account_id` int(11) NOT NULL,
`start` DATETIME NOT NULL,
`end` DATETIME NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
CREATE TABLE `dates` (
`date` date NOT NULL,
PRIMARY KEY (`date`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
日期表包含2010-1-1至2020-1-1(~3k行)的所有日期。访问表包含从2010年6月1日到昨天的约400k行。我正在使用日期表,因此连接将在没有访问的情况下返回0次访问。
结果我想参考:
+------------+--------+
| date | visits |
+------------+--------+
| 2010-12-13 | 301 |
| 2010-12-14 | 356 |
| 2010-12-15 | 423 |
| 2010-12-16 | 332 |
| 2010-12-17 | 346 |
| 2010-12-18 | 226 |
| 2010-12-19 | 213 |
| 2010-12-20 | 311 |
| 2010-12-21 | 273 |
| 2010-12-22 | 286 |
| 2010-12-23 | 241 |
| 2010-12-24 | 149 |
| 2010-12-25 | 102 |
| 2010-12-26 | 174 |
| 2010-12-27 | 258 |
| 2010-12-28 | 348 |
| 2010-12-29 | 392 |
| 2010-12-30 | 395 |
| 2010-12-31 | 278 |
| 2011-01-01 | 241 |
| 2011-01-02 | 295 |
| 2011-01-03 | 369 |
| 2011-01-04 | 438 |
| 2011-01-05 | 393 |
| 2011-01-06 | 368 |
| 2011-01-07 | 435 |
| 2011-01-08 | 313 |
| 2011-01-09 | 250 |
| 2011-01-10 | 345 |
| 2011-01-11 | 387 |
| 2011-01-12 | 0 |
| 2011-01-13 | 0 |
+------------+--------+
提前感谢您的帮助!
答案 0 :(得分:4)
你的问题在这里:
ON (dates.date = DATE(visits.start) and account_id = 40 )
因为您在DATE
上使用visits.start
函数,所以MySQL无法使用索引进行连接。
最好的解决方案可能是在start_date
表中添加end_date
和dates
列并为这些列编制索引。因此,对于日期为2011-01-01的行,开始日期为2011-01-01 00:00:00,结束日期为2011-01-01 23:59:59。
然后你可以像这样直接加入日期表:
SELECT date, count(id) as 'visits' FROM dates
LEFT OUTER JOIN visits
ON (visits.start BETWEEN dates.start_date AND dates.end_date and account_id = 40 )
WHERE date >= '2010-12-13' AND date <= '2011-1-13'
GROUP BY date ORDER BY date ASC
另一种选择是在访问表上单独存储日期和时间部分,并仅使用日期部分加入。
答案 1 :(得分:0)
我认为由于DATE()函数,它主要是慢的。您可以向存储整个日期的Visits添加日期列,并编写触发器以在插入访问或更新其日期时自动更新它。这将允许MySQL更好地利用连接中使用的索引。
答案 2 :(得分:0)
这样的事情:从eumiro中选择结果的外连接?
SELECT date, v.visits as 'visits' FROM dates
LEFT OUTER JOIN (SELECT DATE(start) as dt, count(id) as 'visits'
FROM visits
WHERE account_id = 40
AND date BETWEEN '2010-12-13' AND '2011-01-13'
GROUP BY DATE(start)
ORDER BY 1)
v
ON (dates.date = v.dt )
WHERE date >= '2010-12-13' AND date <= '2011-1-13'
编辑:编辑过的SQL 编辑:另一个选项 - 内联选择,类似的东西:
SELECT date, (select count(*) as 'visits'
FROM from visits
where date = DATE(visits.start) and account_id = 40 )
) from dates
WHERE date >= '2010-12-13' AND date <= '2011-1-13'
ORDER BY date ASC