MySQL更新子集具有

问题描述

我有三个表:contacts，domains和contacts_domains，它们形成了多对多关系.

I have three tables: contacts, domains, and contacts_domains, which form a many-to-many relationship.

我想运行一个查询，以更新contacts_domains表，但仅适用于仅具有一个联系人的域.

I would like to run a query that updates the contacts_domains table, but only for domains that have exactly one contact.

我知道如何选择我感兴趣的行，但不知道如何更新它们.

I know how to SELECT the rows I'm interested in, but not how to UPDATE them.

SELECT domain_id, contact_id, dominant
FROM contacts_domains
GROUP BY domain_id
HAVING COUNT(contact_id) = 1

我想为所有这些结果设置contacts_domains.dominant = 1.

I want to set contacts_domains.dominant = 1 for all these results.

谢谢！

推荐答案

最简单的解决方案:

UPDATE contacts_domains cd SET cd.dominant = 1
WHERE cd.id IN (
SELECT dominant_id
FROM contacts_domains
GROUP BY domain_id
HAVING COUNT(contact_id) = 1
)

已编辑.

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