SQL 从另一个表中的另一列更新一列

2022-01-17 00:00:00 join sql-update mysql

在此之前我阅读了各种帖子.但它们似乎都不适合我.

I read various post's prior to this. but none of them seemed to work for me.

正如标题所示，我正在尝试从另一个表中的一列更新一列.我不记得以前有这个问题..

As the title suggests, I am trying to update one column from a column in another table. I don't recall having problems with this before..

1.表:user_settings.contact_id，我想用contacts.id更新where (user_settings.account_id == contacts_account_id)

1. Table: user_settings.contact_id, I want to update with contacts.id where (user_settings.account_id == contacts_account_id)

2. 以前，联系人是通过 account_id 链接到用户帐户的.但是，现在我们想通过 contacts.id

2. Previously Contacts were linked to user accounts via the account_id. However, now we want to link a contact to user_settings via contacts.id

以下是我尝试过的一些示例，尽管它们都没有奏效.我会对 A.) 为什么它们不起作用和 B.) 我应该怎么做.

Below are a few examples of what I have tried, though none of them have worked. I would be interested in A.) Why they don't work and B.) What should I do instead.

示例 A:

UPDATE user_settings
SET user_settings.contact_id = contacts.id 
FROM user_settings 
INNER JOIN contacts ON user_settings.account_id = contacts.account_id

示例 B:

UPDATE (SELECT A.contact_id id1, B.id id2
  FROM user_settings A, contacts B
  WHERE user_settings.account_id = contacts.account_id)
SET id1 = id2

示例 C:

UPDATE user_settings
SET user_settings.contact_id = (SELECT id
  FROM contacts
  WHERE (user_settings.account_id = contacts.account_id)
WHERE EXISTS ( user_settings.account_id = contacts.account_id )

我觉得我的大脑刚刚对我关闭，如果有任何颠簸重新启动它，我将不胜感激.谢谢:)

I feel like my brain just shutdown on me and would appreciate any bumps to reboot it. Thanks :)

推荐答案

根据 MySQL 文档，要进行交叉表更新，您不能使用连接(就像在其他数据库中一样)，而是使用 where 子句:

According to MySQL documentation, to do a cross table update, you can't use a join (like in other databases), but instead use a where clause:

http://dev.mysql.com/doc/refman/5.0/en/update.html

我认为这样的事情应该可行:

I think something like this should work:

UPDATE User_Settings, Contacts
    SET User_Settings.Contact_ID = Contacts.ID
    WHERE User_Settings.Account_ID = Contacts.Account_ID

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