MySQL left outer join is slow
- by Ryan Doherty
Hi, hoping to get some help with this query, I've worked at it for a while now and can't get it any faster:
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
That query takes about 8 seconds to run. I've added indexes on dates.date, visits.start, visits.account_id and visits.start+visits.account_id and can't get it to run any faster.
Table structure (only showing relevant columns in visit table):
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;
dates table contains all days from 2010-1-1 to 2020-1-1 (~3k rows). visits table contains about 400k rows dating from 2010-6-1 to yesterday. I'm using the date table so the join will return 0 visits for days there were no visits.
Results I want for reference:
+------------+--------+
| 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 |
+------------+--------+
Thanks in advance for any help!
