[英]How to perform optimal FULL OUTER JOIN on more than two MySQL tables?
首先，我想说的是，我已经发现MySQL不支持SQL的FULL OUTER JOIN 。 但是，我需要以这种方式连接数据...希望我说对了，我说“我需要FULL OUTER JOIN”。 如果我错了，请纠正我。
我的情况是什么？ 一张桌子（ users ）描述了注册玩游戏的用户。 表results1描述了用户玩的Game1的结果，表results2描述了用户的结果玩游戏2等。
现在，我想编写一个查询，以获取一段时间内所有游戏的用户和用户点的列表。 点数必须加总。 该查询必须按user_id和日期（每月）对结果进行分组。
最大的问题是，任何一个表都没有完整的月份数（因此我不能仅执行LEFT或RIGHT连接）。 我考虑过要制作某种类型的临时日历表（一段时间内只有几年和几个月），然后将带有点（ results1 ， results2 ， results3等等）的表连接到该日历表。 但是这种解决方案似乎也很复杂。 还有其他想法吗？
我的情况（MySQL转储）：
-- --------------------------------------------------------
-- Host: 192.168.0.60
-- Server version: 5.5.40-cll-lve - MySQL Community Server (GPL) by Atomicorp
-- Server OS: Linux
-- HeidiSQL Version: 9.1.0.4867
-- --------------------------------------------------------
/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET NAMES utf8mb4 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
-- Dumping database structure for example
CREATE DATABASE IF NOT EXISTS `example` /*!40100 DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci */;
USE `example`;
-- Dumping structure for table example.results1
CREATE TABLE IF NOT EXISTS `results1` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(11) DEFAULT NULL,
`points` int(11) DEFAULT NULL,
`date` date DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
-- Dumping data for table example.results1: ~8 rows (approximately)
/*!40000 ALTER TABLE `results1` DISABLE KEYS */;
INSERT INTO `results1` (`id`, `user_id`, `points`, `date`) VALUES
(1, 1, 5, '2014-01-17'),
(2, 1, 5, '2014-01-18'),
(3, 2, 10, '2014-02-17'),
(4, 9, 8, '2014-03-17'),
(5, 1, 15, '2014-07-17'),
(6, 3, 9, '2014-10-17'),
(7, 1, 20, '2015-02-17'),
(8, 5, 10, '2014-06-17');
/*!40000 ALTER TABLE `results1` ENABLE KEYS */;
-- Dumping structure for table example.results2
CREATE TABLE IF NOT EXISTS `results2` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(11) DEFAULT NULL,
`points` int(11) DEFAULT NULL,
`date` date DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ROW_FORMAT=COMPACT;
-- Dumping data for table example.results2: ~8 rows (approximately)
/*!40000 ALTER TABLE `results2` DISABLE KEYS */;
INSERT INTO `results2` (`id`, `user_id`, `points`, `date`) VALUES
(1, 1, 50, '2014-01-01'),
(2, 2, 35, '2014-01-02'),
(3, 3, 14, '2014-01-03'),
(4, 4, 18, '2014-06-01'),
(5, 5, 16, '2014-06-01'),
(6, 5, 16, '2014-06-02'),
(7, 6, 4, '2014-10-29'),
(8, 1, 20, '2014-01-16');
/*!40000 ALTER TABLE `results2` ENABLE KEYS */;
-- Dumping structure for table example.results3
CREATE TABLE IF NOT EXISTS `results3` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(11) DEFAULT NULL,
`points` int(11) DEFAULT NULL,
`date` date DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ROW_FORMAT=COMPACT;
-- Dumping data for table example.results3: ~3 rows (approximately)
/*!40000 ALTER TABLE `results3` DISABLE KEYS */;
INSERT INTO `results3` (`id`, `user_id`, `points`, `date`) VALUES
(1, 9, 6, '2014-12-17'),
(2, 1, 10, '2014-01-01'),
(3, 1, 2, '2014-10-17'),
(4, 1, 8, '2014-01-03');
/*!40000 ALTER TABLE `results3` ENABLE KEYS */;
-- Dumping structure for table example.results4
CREATE TABLE IF NOT EXISTS `results4` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(11) DEFAULT NULL,
`points` int(11) DEFAULT NULL,
`date` date DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ROW_FORMAT=COMPACT;
-- Dumping data for table example.results4: ~2 rows (approximately)
/*!40000 ALTER TABLE `results4` DISABLE KEYS */;
INSERT INTO `results4` (`id`, `user_id`, `points`, `date`) VALUES
(1, 4, 41, '2015-03-17'),
(2, 1, 2, '2014-12-17');
/*!40000 ALTER TABLE `results4` ENABLE KEYS */;
-- Dumping structure for table example.users
CREATE TABLE IF NOT EXISTS `users` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(1000) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
-- Dumping data for table example.users: ~10 rows (approximately)
/*!40000 ALTER TABLE `users` DISABLE KEYS */;
INSERT INTO `users` (`id`, `name`) VALUES
(1, 'Sophie'),
(2, 'Joshua'),
(3, 'Isabelle'),
(4, 'Jack'),
(5, 'Emily'),
(6, 'Harry'),
(7, 'Olivia'),
(8, 'Oliver'),
(9, 'Lily'),
(10, 'Charlie');
/*!40000 ALTER TABLE `users` ENABLE KEYS */;
/*!40101 SET SQL_MODE=IFNULL(@OLD_SQL_MODE, '') */;
/*!40014 SET FOREIGN_KEY_CHECKS=IF(@OLD_FOREIGN_KEY_CHECKS IS NULL, 1, @OLD_FOREIGN_KEY_CHECKS) */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
我要联接两个表的查询：
SELECT
r1_r2.user_id, r1_r2.points, r1_r2.`date`
FROM (
SELECT
IFNULL(rr1.user_id, rr2.user_id) as user_id, (IFNULL(rr1.points,0) + IFNULL(rr2.points,0)) as points, IFNULL(rr1.`date`, rr2.`date`) as `date`
FROM (
SELECT
r1.user_id, SUM(r1.points) as points, DATE_FORMAT(r1.`date`, '%Y-%m') as `date`
FROM results1 as r1
GROUP BY r1.user_id, DATE_FORMAT(r1.`date`, '%Y-%m')
) as rr1
LEFT JOIN (
SELECT
r2.user_id, SUM(r2.points) as points, DATE_FORMAT(r2.`date`, '%Y-%m') as `date`
FROM results2 as r2
GROUP BY r2.user_id, DATE_FORMAT(r2.`date`, '%Y-%m')
) as rr2 ON (rr1.user_id = rr2.user_id AND rr1.`date` = rr2.`date`)
UNION
SELECT
IFNULL(rl1.user_id, rl2.user_id) as user_id, (IFNULL(rl1.points,0) + IFNULL(rl2.points,0)) as points, IFNULL(rl1.`date`, rl2.`date`) as `date`
FROM (
SELECT
r1.user_id, SUM(r1.points) as points, DATE_FORMAT(r1.`date`, '%Y-%m') as `date`
FROM results1 as r1
GROUP BY r1.user_id, DATE_FORMAT(r1.`date`, '%Y-%m')
) as rl1
RIGHT JOIN (
SELECT
r2.user_id, SUM(r2.points) as points, DATE_FORMAT(r2.`date`, '%Y-%m') as `date`
FROM results2 as r2
GROUP BY r2.user_id, DATE_FORMAT(r2.`date`, '%Y-%m')
) as rl2 ON (rl1.user_id = rl2.user_id AND rl1.`date` = rl2.`date`)
) as r1_r2
HAVING
r1_r2.`date` BETWEEN '2014-01' AND '2014-12'
ORDER BY
r1_r2.user_id ASC, r1_r2.`date` ASC
它适用于两个表（ results1和results2 ），但是问题是我需要两个以上的表以相同的方式进行连接...
我对此有某种解决方案（例如一遍又一遍嵌套表格），但是问题是我的解决方案也变得非常复杂（篇幅长，阅读和理解非常复杂）。 此外，在不久的将来还有可能出现一些其他表格。 添加额外的3或5个表后，查询的外观如何？ 如果我继续进行相同的嵌套联接，则整个查询将变得越来越复杂，难以阅读，理解，修改...
这是对3个联接的表（ results1 ， results2 ， results3 ）的查询：
SELECT
r1_r2_r3.user_id, r1_r2_r3.points, r1_r2_r3.`date`
FROM (
SELECT
IFNULL(r1_r2_l.user_id, r3_l.user_id) as user_id, (IFNULL(r1_r2_l.points,0) + IFNULL(r3_l.points,0)) as points, IFNULL(r1_r2_l.`date`, r3_l.`date`) as `date`
FROM (
# BEGIN. RESULT FROM BEFORE
SELECT
r1_r2.user_id, r1_r2.points, r1_r2.`date`
FROM (
SELECT
IFNULL(rr1.user_id, rr2.user_id) as user_id, (IFNULL(rr1.points,0) + IFNULL(rr2.points,0)) as points, IFNULL(rr1.`date`, rr2.`date`) as `date`
FROM (
SELECT
r1.user_id, SUM(r1.points) as points, DATE_FORMAT(r1.`date`, '%Y-%m') as `date`
FROM results1 as r1
GROUP BY r1.user_id, DATE_FORMAT(r1.`date`, '%Y-%m')
) as rr1
LEFT JOIN (
SELECT
r2.user_id, SUM(r2.points) as points, DATE_FORMAT(r2.`date`, '%Y-%m') as `date`
FROM results2 as r2
GROUP BY r2.user_id, DATE_FORMAT(r2.`date`, '%Y-%m')
) as rr2 ON (rr1.user_id = rr2.user_id AND rr1.`date` = rr2.`date`)
UNION
SELECT
IFNULL(rl1.user_id, rl2.user_id) as user_id, (IFNULL(rl1.points,0) + IFNULL(rl2.points,0)) as points, IFNULL(rl1.`date`, rl2.`date`) as `date`
FROM (
SELECT
r1.user_id, SUM(r1.points) as points, DATE_FORMAT(r1.`date`, '%Y-%m') as `date`
FROM results1 as r1
GROUP BY r1.user_id, DATE_FORMAT(r1.`date`, '%Y-%m')
) as rl1
RIGHT JOIN (
SELECT
r2.user_id, SUM(r2.points) as points, DATE_FORMAT(r2.`date`, '%Y-%m') as `date`
FROM results2 as r2
GROUP BY r2.user_id, DATE_FORMAT(r2.`date`, '%Y-%m')
) as rl2 ON (rl1.user_id = rl2.user_id AND rl1.`date` = rl2.`date`)
) as r1_r2
# END. RESULT FROM BEFORE
) as r1_r2_l
LEFT JOIN (
SELECT
r3.user_id, SUM(r3.points) as points, DATE_FORMAT(r3.`date`, '%Y-%m') as `date`
FROM results3 as r3
GROUP BY r3.user_id, DATE_FORMAT(r3.`date`, '%Y-%m')
) as r3_l ON (r1_r2_l.user_id = r3_l.user_id AND r1_r2_l.`date` = r3_l.`date`)
UNION
SELECT
IFNULL(r1_r2_r.user_id, r3_r.user_id) as user_id, (IFNULL(r1_r2_r.points,0) + IFNULL(r3_r.points,0)) as points, IFNULL(r1_r2_r.`date`, r3_r.`date`) as `date`
FROM (
# BEGIN. RESULT FROM BEFORE
SELECT
r1_r2.user_id, r1_r2.points, r1_r2.`date`
FROM (
SELECT
IFNULL(rr1.user_id, rr2.user_id) as user_id, (IFNULL(rr1.points,0) + IFNULL(rr2.points,0)) as points, IFNULL(rr1.`date`, rr2.`date`) as `date`
FROM (
SELECT
r1.user_id, SUM(r1.points) as points, DATE_FORMAT(r1.`date`, '%Y-%m') as `date`
FROM results1 as r1
GROUP BY r1.user_id, DATE_FORMAT(r1.`date`, '%Y-%m')
) as rr1
LEFT JOIN (
SELECT
r2.user_id, SUM(r2.points) as points, DATE_FORMAT(r2.`date`, '%Y-%m') as `date`
FROM results2 as r2
GROUP BY r2.user_id, DATE_FORMAT(r2.`date`, '%Y-%m')
) as rr2 ON (rr1.user_id = rr2.user_id AND rr1.`date` = rr2.`date`)
UNION
SELECT
IFNULL(rl1.user_id, rl2.user_id) as user_id, (IFNULL(rl1.points,0) + IFNULL(rl2.points,0)) as points, IFNULL(rl1.`date`, rl2.`date`) as `date`
FROM (
SELECT
r1.user_id, SUM(r1.points) as points, DATE_FORMAT(r1.`date`, '%Y-%m') as `date`
FROM results1 as r1
GROUP BY r1.user_id, DATE_FORMAT(r1.`date`, '%Y-%m')
) as rl1
RIGHT JOIN (
SELECT
r2.user_id, SUM(r2.points) as points, DATE_FORMAT(r2.`date`, '%Y-%m') as `date`
FROM results2 as r2
GROUP BY r2.user_id, DATE_FORMAT(r2.`date`, '%Y-%m')
) as rl2 ON (rl1.user_id = rl2.user_id AND rl1.`date` = rl2.`date`)
) as r1_r2
# END. RESULT FROM BEFORE
) as r1_r2_r
RIGHT JOIN (
SELECT
r3.user_id, SUM(r3.points) as points, DATE_FORMAT(r3.`date`, '%Y-%m') as `date`
FROM results3 as r3
GROUP BY r3.user_id, DATE_FORMAT(r3.`date`, '%Y-%m')
) as r3_r ON (r1_r2_r.user_id = r3_r.user_id AND r1_r2_r.`date` = r3_r.`date`)
) as r1_r2_r3
HAVING
r1_r2_r3.`date` BETWEEN '2014-01' AND '2014-12'
ORDER BY
r1_r2_r3.user_id ASC, r1_r2_r3.`date` ASC
...我想通过说如果我们继续使用相同的方式继续连接更多的表，查询将变得非常复杂，这可以理解我的意思。
顺便说一下，这只是真实情况的简化版本。 在现实中， results1 ， results2 ， results3和results4已经通过加入其他表，计算之间有值表...所以最终的查询我必须工作在比上面的例子中提到的要复杂得多。
我的问题是： 我可以使联接两个以上表的查询更短，更容易理解吗？
我认为您可以使用union all和聚合来执行您想要的操作。 我认为以下是您想要的：
select user_id, year(date), month(date), sum(points1) as point31,
sum(points2) as points2, sum(points3) as points3
from users u left join
((select r1.user_id, r1.date, r1.points as points1, NULL as points2, NULL as points3
from results1 r1
) union all
(select r2.user_id, r2.date, NULL as points1, r2.points as points2, NULL as points3
from results2 r2
) union all
(select r3.user_id, r3.date, NULL as points1, NULL as points2, r3.points as points3
from results3 r3
)
) r
on u.id = r.user_id
group by user_id, year(date), month(date);
如何在MySQL中格式化两个以上表的FULL OUTER JOIN？
[英]How to format a FULL OUTER JOIN for more than two tables in mySQL?
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