Mysql与group_by语句相反
我有以下架构：
这个概念是这样的： 我们有卖家和买家。卖家创建任务，买家发起聊天并开始对话。因此，卖家可以与不同的买家进行多次聊天（每个买家一次聊天，买家只能发起一次聊天，但他可以发送许多消息），聊天会有很多消息。该邮件具有author_id，无论是卖方还是买方。
所以我想找到两件事（两个查询）： 一个是我想找到所有没有使用author_id的消息的任务等于tasks.seller_id（或根本没有消息）。
其次，我想找到相反的，至少有一条消息，其中author_id等于seller_id。第二个是查询（感谢@ bill-karwin）：
SELECT t.id, COUNT(*) AS sellerMessages
FROM tasks AS t
INNER JOIN chats AS c ON c.task_id = t.id
INNER JOIN messages AS m ON m.chat_id = c.id
AND t.seller_id = m.author_id
GROUP BY t.id
HAVING sellerMessages > 0
ORDER BY t.id;
我怎样才能找到相反的结果？
更新
我已经粘贴了一个带有记录的sql脚本来测试：http://pastebin.com/KmMJjQsR 它创建了60个不同的任务记录及其消息和聊天关联。
上面的sql查询返回31个任务，这是正确的。我需要找到与上面相反的内容，它将返回其他29个任务。
创建脚本
DROP TABLE IF EXISTS `tasks`;
CREATE TABLE `tasks` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`seller_id` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `index_tasks_on_seller_id` (`seller_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `tasks` (`id`, `seller_id`)
VALUES
(15788, 95157),
(15789, 95158),
(15790, 86270),
(15791, 86270),
(15792, 94260),
(15793, 14354),
(15794, 95160),
(15795, 95161),
(15796, 10786),
(15797, 95162),
(15798, 72740),
(15799, 95163),
(15800, 93159),
(15801, 95165),
(15802, 95168),
(15803, 95170),
(15804, 95173),
(15805, 6983),
(15806, 95175),
(15807, 95177),
(15808, 80037),
(15809, 45066),
(15810, 95180),
(15811, 95181),
(15812, 95182),
(15813, 84020),
(15814, 95156),
(15815, 93418),
(15816, 74020),
(15817, 74020),
(15818, 73604),
(15819, 95190),
(15820, 95188),
(15821, 39132),
(15822, 95191),
(15823, 95192),
(15824, 95196),
(15825, 32979),
(15826, 30104),
(15827, 95198),
(15828, 95200),
(15829, 93974),
(15830, 95201),
(15831, 95202),
(15832, 33487),
(15833, 60076),
(15834, 33487),
(15835, 88081),
(15836, 95204),
(15837, 95205),
(15838, 27527),
(15839, 93055),
(15840, 95209),
(15841, 2297),
(15842, 95211),
(15843, 76806),
(15844, 69400),
(15845, 34273),
(15846, 95214),
(15847, 82877);
DROP TABLE IF EXISTS `chats`;
CREATE TABLE `chats` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`creator_id` int(11) DEFAULT NULL,
`task_id` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `chats` (`id`, `creator_id`, `task_id`)
VALUES
(10754, 53058, 15788),
(10767, 36414, 15788),
(10778, 61359, 15788),
(10759, 61359, 15789),
(10770, 36414, 15789),
(10961, 10541, 15790),
(10777, 61359, 15792),
(10819, 11835, 15793),
(10766, 4631, 15795),
(10791, 18461, 15795),
(10823, 31111, 15795),
(10874, 11649, 15795),
(10994, 85902, 15795),
(10769, 36414, 15797),
(10776, 61359, 15797),
(10919, 53058, 15797),
(10771, 12815, 15798),
(10775, 83339, 15798),
(10811, 12745, 15799),
(11211, 35416, 15799),
(10793, 4631, 15800),
(10833, 85902, 15800),
(10816, 36414, 15802),
(10806, 36414, 15803),
(10801, 80049, 15804),
(10818, 36414, 15804),
(10824, 11835, 15805),
(10802, 7240, 15806),
(10822, 39871, 15806),
(10838, 79168, 15806),
(10817, 36414, 15807),
(10918, 53058, 15807),
(10809, 33051, 15808),
(10843, 20435, 15808),
(10803, 45069, 15809),
(10804, 5093, 15809),
(10814, 84699, 15810),
(10844, 58098, 15810),
(10847, 95206, 15810),
(10849, 95105, 15810),
(10853, 94009, 15810),
(10854, 94009, 15810),
(10855, 94009, 15810),
(10856, 94009, 15810),
(10857, 94009, 15810),
(10858, 94009, 15810),
(10859, 94009, 15810),
(10860, 94009, 15810),
(10894, 65435, 15814),
(11057, 91171, 15815),
(10975, 85902, 15816),
(10812, 4631, 15817),
(10841, 85115, 15818),
(10903, 87971, 15818),
(10980, 36414, 15819),
(10886, 39393, 15821),
(10825, 11835, 15824),
(10871, 2919, 15824),
(11194, 21322, 15824),
(11137, 94553, 15825),
(10831, 84932, 15826),
(10836, 83339, 15826),
(10839, 8532, 15826),
(10840, 11967, 15826),
(10913, 35573, 15827),
(10983, 36414, 15827),
(10878, 29425, 15829),
(10952, 36414, 15831),
(10845, 10511, 15832),
(10941, 7240, 15832),
(10872, 3154, 15834),
(10897, 36414, 15835),
(10917, 53058, 15835),
(11045, 36902, 15835),
(10879, 29425, 15836),
(11114, 94682, 15836),
(10900, 36414, 15837),
(10846, 4631, 15838),
(10850, 4631, 15839),
(10848, 4631, 15841),
(10852, 4631, 15842),
(10851, 4631, 15844),
(10864, 62822, 15845),
(10889, 85115, 15847);
DROP TABLE IF EXISTS `messages`;
CREATE TABLE `messages` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`chat_id` int(11) DEFAULT NULL,
`author_id` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `messages` (`chat_id`, `author_id`)
values
(10754, 53058),
(10767, 36414),
(10778, 61359),
(10759, 61359),
(10759, 95158),
(10770, 36414),
(10770, 95158),
(10961, 10541),
(10961, 86270),
(10777, 61359),
(10819, 11835),
(10819, 14354),
(10766, 4631),
(10766, 95161),
(10791, 95161),
(10791, 18461),
(10823, 31111),
(10874, 11649),
(10994, 85902),
(10769, 36414),
(10776, 61359),
(10919, 53058),
(10775, 83339),
(10775, 72740),
(10811, 12745),
(10811, 95163),
(11211, 35416),
(11211, 95163),
(10793, 4631),
(10793, 93159),
(10833, 85902),
(10833, 93159),
(10816, 36414),
(10806, 36414),
(10801, 80049),
(10818, 36414),
(10824, 11835),
(10824, 6983),
(10802, 7240),
(10802, 95175),
(10822, 39871),
(10838, 79168),
(10838, 95175),
(10817, 36414),
(10817, 95177),
(10918, 53058),
(10809, 33051),
(10809, 80037),
(10843, 20435),
(10843, 80037),
(10803, 45069),
(10804, 5093),
(10814, 84699),
(10814, 95180),
(10844, 58098),
(10844, 95180),
(10847, 95206),
(10847, 95180),
(10849, 95105),
(10849, 95180),
(10853, 94009),
(10853, 95180),
(10894, 65435),
(10894, 95156),
(11057, 91171),
(10975, 85902),
(10975, 74020),
(10812, 4631),
(10812, 74020),
(10841, 85115),
(10841, 73604),
(10903, 87971),
(10903, 73604),
(10980, 36414),
(10980, 95190),
(10886, 39393),
(10886, 39132),
(10825, 11835),
(10825, 95196),
(10871, 2919),
(10871, 95196),
(11194, 21322),
(11194, 95196),
(11137, 94553),
(10831, 84932),
(10836, 83339),
(10839, 8532),
(10839, 30104),
(10840, 11967),
(10913, 35573),
(10913, 95198),
(10983, 36414),
(10878, 29425),
(10878, 93974),
(10952, 36414),
(10845, 33487),
(10845, 10511),
(10941, 7240),
(10872, 3154),
(10872, 33487),
(10897, 36414),
(10897, 88081),
(10917, 53058),
(11045, 36902),
(11045, 88081),
(10879, 29425),
(10879, 95204),
(11114, 94682),
(10900, 36414),
(10900, 95205),
(10846, 4631),
(10846, 27527),
(10850, 4631),
(10850, 93055),
(10848, 4631),
(10852, 4631),
(10852, 95211),
(10851, 4631),
(10851, 69400),
(10864, 62822),
(10889, 85115);
结果：
在一个查询（包含邮件中包含sender_id的查询）中，应返回31或作业ID
15789,15790,15793,15795,15798,15799,15800,
15805,15806,15807,15808,15810,15814,15816,
15817,15818,15819,15821,15824,15826,15827,
15829,15832,15834,15835,15836,15837,15838,
15839,15842,15844
在另一个查询中，结果应为
15841,15796,15825,15845,15809,15833,15843,
15847,15813,15791,15815,15792,15788,15794,
15797,15801,15802,15803,15804,15811,15812,
15820,15822,15823,15828,15830,15831,15840,15846
或29。
2 个答案:
答案 0 :(得分：1)
我想找到所有没有使用author_id的消息的任务等于tasks.seller_id（或根本没有消息）。
以下是我的写作方式：
SELECT t.id
FROM tasks AS t
LEFT OUTER JOIN chats AS c ON c.task_id = t.id
LEFT OUTER JOIN messages AS m ON m.chat_id = c.id
AND t.seller_id = m.author_id
WHERE m.chat_id IS NULL
ORDER BY t.id;
我想找到相反的任务，其中至少有一条消息，其中author_id等于seller_id。
以下是我的写作方式：
SELECT t.id
, COUNT(*) AS sellerMessages
FROM tasks AS t
INNER JOIN chats AS c ON c.task_id = t.id
INNER JOIN messages AS m ON m.chat_id = c.id
AND t.seller_id = m.author_id
GROUP BY t.id
HAVING sellerMessages > 0
ORDER BY t.id;
答案 1 :(得分：1)
我想找到至少有一条消息的...任务
author_id等于seller_id。
您对问题的疑问可以简化一下。不需要明确的HAVING过滤器，因为INNER JOINs会这样做。如果您不需要消息数，则可以省略COUNT。
SELECT t.id
FROM tasks AS t
INNER JOIN chats AS c ON c.task_id = t.id
INNER JOIN messages AS m
ON m.chat_id = c.id
AND t.seller_id = m.author_id
GROUP BY t.id
ORDER BY t.id;
我想找到所有 没有
author_id等于的消息的任务tasks.seller_id（或根本没有消息）。
获得与顶级查询相反的一种非常直接的方法是将其用作NOT IN的子查询：
SELECT tasks.id
FROM tasks
WHERE
tasks.id NOT IN
(
SELECT t.id
FROM tasks AS t
INNER JOIN chats AS c ON c.task_id = t.id
INNER JOIN messages AS m
ON m.chat_id = c.id
AND t.seller_id = m.author_id
)
;
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