Mysql:更新最新记录的字段

Mysql: Update field of most latest record(Mysql:更新最新记录的字段)

问题描述

我正在尝试更新名称为 John 的最新记录(John 有多个记录但 ID 不同)，但我似乎处于绑定状态.我的查询有什么问题?

I'm trying to update the latest record where name is John (John has multiple records but different ID) but I seem to be in a bind. What's wrong with my query?

UPDATE messages_tbl SET is_unread=1
WHERE ReceiveTime = (SELECT MAX(ReceiveTime) FROM messages_tbl WHERE name='John')

有没有更好的方法来做这样的事情?

Is there a better way to do something like this?

推荐答案

可以同时加入，根据条件进行更新.

You can join both and perform update based on the condition.

UPDATE  messages a
        INNER JOIN
        (
            SELECT  name , MAX(ReceiveTime) max_time
            FROM    messages 
            GROUP   BY name 
        ) b ON  a.name = b.name AND
                a.ReceiveTime = b.max_time
SET     a.is_unread = 1
-- WHERE    a.name = 'John'

没有 WHERE 条件.它将全部更新列 is_unread 以获取最新条目.

Without the WHERE condition. It will all update the column is_unread for the latest entry.

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