选择具有唯一列值的行

Question

我正在尝试编写一个 SQL 命令 returns emails 具有值 (track openers) 并且没有值 (redirect) 对于同一 table 中的列 action_type。

email              countrycode    action_type
email1@domain.com  GB             track openers
email1@domain.com  GB             redirect
email2@domain.com  GB             track openers
email2@domain.com  GB             redirect
email3@domain.com  GB             track openers
email3@domain.com  GB             redirect
email4@domain.com  GB             track openers <<

DB Table Screenshot

我已经尝试过了，但没有成功，它继续显示正在加载...没有返回任何结果

SELECT DISTINCT LOWER(email) as `email`, `action_type`, `countrycode`
FROM `stats`
WHERE `email` NOT IN (SELECT `email` FROM `stats` WHERE `action_type` = 'redirect');

Answer 1

我建议聚合：

SELECT LOWER(email) as email
FROM `stats`
WHERE action_type in ('redirect', 'track openers')
GROUP BY LOWER(email)
HAVING MIN(action_type) = MAX(action_type) AND
       MIN(action_type) = 'track openers';

Answer 2

这也是一种选择。在这里您可以查找所有具有操作类型 track openers 且不存在具有 redirect 操作类型的操作的电子邮件。

SELECT LOWER(email)
FROM stats s
WHERE s.action_type = 'track openers' AND NOT EXISTS(
    SELECT ss.email
    FROM stats ss
    WHERE s.email = ss.email
    AND ss.action_type = 'redirect'
);

Answer 3

稍微不那么冗长的选项

SELECT LOWER(email) as email
FROM `stats`
WHERE action_type in ('redirect', 'track openers') --optional if there are only 2 types
GROUP BY email
HAVING AVG(CASE WHEN action_type ='track openers' THEN 1 END) = 1;

选择具有唯一列值的行

Selecting rows with unique column values

sql

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