MySQL-正确的进近事件计数 [英] MySQL - Correct approach event counting

问题描述

我想列出具有特定事件计数的用户，但是我对采用哪种方法感到困惑.

I want to list users which have a particular event count but I'm confused on which approach to take.

这是数据库表:

CREATE TABLE `event` (
  `event_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `visitor_id` int(11) DEFAULT NULL,
  `key` varchar(200) DEFAULT NULL,
  `value` text,
  `label` varchar(200) DEFAULT '',
  `datetime` datetime DEFAULT NULL,
  PRIMARY KEY (`event_id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;


INSERT INTO `event` (`event_id`, `visitor_id`, `key`, `value`, `label`, `datetime`)
VALUES
    (1, 1, 'LOGIN', NULL, '', NULL),
    (2, 2, 'LOGIN', NULL, '', NULL),
    (3, 1, 'VIEW_PAGE', 'HOTEL', '', NULL),
    (4, 2, 'VIEW_PAGE', 'HOTEL', '', NULL),
    (5, 1, 'PURCHASE_HOTEL', NULL, '', NULL);

CREATE TABLE `visitor` (
  `visitor_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `datetime` datetime DEFAULT NULL,
  PRIMARY KEY (`visitor_id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

INSERT INTO `visitor` (`visitor_id`, `datetime`)
VALUES
    (1, NULL),
    (2, NULL);

这是我的方法:

SELECT DISTINCT
    t1.`visitor_id`
FROM
    `visitor` t1

JOIN `event` t2 on t1.visitor_id = t2.visitor_id AND t2.`key` = 'LOGIN'
JOIN `event` t3 on t1.visitor_id = t3.visitor_id AND t3.`key` = 'VIEW_PAGE' AND t3.`value` = 'HOTEL'
WHERE ( SELECT COUNT(*) FROM `event` WHERE `event`.`key` = 'PURCHASE_HOTEL' ) > 0

这应该只列出访问者1，但是实际上也列出没有PURCHASE_HOTEL事件的访问者2.

this should only list visitor 1 but it does actually list visitor 2 too which does not have the PURCHASE_HOTEL event.

您可以想象，对于每个特定案例，将有更多的规则"，如所有JOIN事件.我们可以以某种方式纠正和改进吗?

As you can imagine, there will be more "rules" like all the JOIN events for each particular case. Can we correct and improve this somehow?

奖金: 这种方法的名称是什么?

BONUS: What is the name of this approach?

推荐答案

我认为这是集内集"查询.我喜欢对这种类型的查询使用带有having子句的聚合.以下内容将检查您要查找的三个条件:

I think this is a "set-within-sets" query. I like using aggregation with a having clause for this type of query. The following checks the three conditions you are looking for:

select visitor_id
from event e
group by visitor_id
having sum(e.key = 'LOGIN') > 0 and
       sum(e.key = 'VIEW_PAGE' and e.value = 'HOTEL') > 0 and
       sum(e.key = 'PURCHASE_HOTEL') > 0;

having子句中的第一个条件对LOGIN记录的数量进行计数，并且在找到至少一个条件时为true. (如果您只想要一个，请将> 0更改为= 0.)

The first condition in the having clause counts the number of LOGIN records and is true when at least one is found. (If you want exactly one, change > 0 to = 0.)

第二个条件检查了酒店页面的浏览情况.

The second condition checks the viewing of the hotel page.

第三位计算的是酒店购买次数.

The third counts the number of hotel purchases.

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