[英]SQL count number of rows in unique combinations of key value columns
Given the following MySQL table structure: 给定以下MySQL表结构:
CREATE TABLE `order_params`( `order_id` BIGINT(30) NOT NULL,
`key` VARCHAR(50) NOT NULL, `value` VARCHAR(255) NOT NULL );
And this data: 这个数据:
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('1', 'browser', 'Firefox');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('1', 'os', 'Windows');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('2', 'browser', 'Firefox');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('2', 'os', 'Windows');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('3', 'browser', 'Firefox');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('3', 'os', 'OSX');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('4', 'browser', 'Safari');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('4', 'os', 'OSX');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('5', 'browser', 'Safari');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('5', 'os', 'OSX');
INSERT INTO `order_params` (`order_id`, `key`, `value`) VALUES ('5', 'version', '5');
How do I get the following results? 我如何获得以下结果?
browser Firefox os Windows 2
browser Firefox os OSX 1
browser Safari os OSX 1
browser Safari os OSX version 5 1
The numbers on the right are the count of records that match the unique key/value combinations. 右侧的数字是与唯一键/值组合匹配的记录数。 Is this even possible?
这甚至可能吗?
OK, updating to show that I have tried this: 好的,更新以显示我已经尝试过:
SELECT CONCAT(`key`, `value`), COUNT(*)
FROM order_params
GROUP BY `order_id`, `key`, `value`;
And this is the result: 这就是结果:
browserFirefox 1
osWindows 1
browserFirefox 1
osWindows 1
browserFirefox 1
osOS X 1
browserSafari 1
osOS X 1
I've also tried this: 我也试过这个:
SELECT `key`, `value`, COUNT(*)
FROM order_params
GROUP BY `key`, `value`;
Which produces this: 产生这个:
browser Firefox 3
browser Safari 1
os OS X 2
os Windows 2
Obviously, neither of these is the desired result. 显然,这些都不是理想的结果。
One approach is two stages of aggregation 一种方法是两个聚合阶段
select browser, os, version, count(*)
from (select order_id,
max(case when `key` = 'browser' then `value` end) as browser,
max(case when `key` = 'os' then `value` end) as os,
max(case when `key` = 'version' then `value` end) as version
from order_params op
group by order_id
) p
group by browser, os, version
If you actually want the string that you have, you can concat things together: 如果你真的想要你拥有的字符串,你可以将它们连在一起:
select concat(coalesce(concat('browser ', browser), ''),
coalesce(concat('os ', os), ''),
coalesce(concat('version ', version), ''), count(*)
from (select order_id,
max(case when `key` = 'browser' then `value` end) as browser,
max(case when `key` = 'os' then `value` end) as os,
max(case when `key` = 'version' then `value` end) as version
from order_params op
group by order_id
) p
group by os, browser, version
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