Question

我有一个电子邮件客户端，其中列出了您在Gmail收件箱中看到的电子邮件。

所有电子邮件都存储在Postgres 9.3.5数据库中。

我想要实现的部分功能是允许用户阻止来自域列表的传入电子邮件，例如@ spam.com，

我有this sqlfiddle，其中包含模式的简化版本，我有一个emails表和一个email_participants表。用户可以选择选择要排除的域名，例如他们可以选择从yahoo.com，hotmail.com等中排除电子邮件。

目前查询基本上是这样的：

SELECT subject, ep.email_id, kind, ep.user_id, ep.contact_id
FROM emails e
INNER JOIN
email_participants ep
ON ep.email_id = e.id
-- and ep.address domain doees not include *.yahoo.com, *.hotmail.com or whatever
WHERE kind = 'sent'
ORDER BY sent_at DESC;

我想将排除的域存储在表中，但我不知道如何从一组数据中使用类似的查询进行排除。

Answer 1

用户可以选择选择要排除的域名

这表明在后端你需要一个具有user_id＆amp;的表。 exclude_domain作为列：

CREATE TABLE user_excludedomain (
    user_id INTEGER NOT NULL,
    domain VARCHAR(255) NOT NULL,
    CONSTRAINT user_excludedomain_pkey PRIMARY KEY (user_id, domain),
    CONSTRAINT user_id_fkey FOREIGN KEY (user_id)
      REFERENCES users (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE CASCADE);

然后在您的选择查询中，将left join添加到此表格＆amp;构造where clause以删除连接从此表中产生一行的行。即

SELECT
    e.subject, 
    ep.email_id,
    e.kind,
    ep.user_id,
    ep.contact_id
FROM emails e
INNER JOIN email_participants ep 
    ON ep.email_id = e.id
-- left join all domains to be excluded
LEFT JOIN user_excludedomain uex 
    ON uex.user_id = ep.user_id 
    AND uex.domain = SUBSTRING(ea.address from '@.*') 
WHERE kind = 'sent'
  AND uex.user_id IS NULL -- pick only rows where the left join returns null (i.e. the excluded domain is not joined)
ORDER BY sent_at DESC;

Answer 2

这可能不完全正确，但足够接近让你到那里......试试：

and substring(ea.address from '@.*') not in ('@yahoo.com', '@hotmail.com')

在上下文中：

SELECT subject, ep.email_id, kind, ep.user_id, ep.contact_id, ea.address
FROM emails e
INNER JOIN
email_participants ep
ON ep.email_id = e.id
JOIN email_addresses ea
ON ep.contact_id = ea.contact_id
and substring(ea.address from '@.*') not in ('@yahoo.com', '@hotmail.com')
WHERE kind = 'sent'
ORDER BY sent_at DESC;

从排除的域列表中排除电子邮件地址

2 个答案: