试试这个
SELECT * FROM messageTable WHERE from_id='abc123' AND `time` = ( SELECT MAX(`time`) FROM messageTable WHERE from_id='abc123' ) UNION ALL SELECT * FROM messageTable WHERE to_id='abc123' AND `time` = ( SELECT MAX(`time`) FROM messageTable WHERE to_id='abc123' )@H_403_5@解决方法
我正在开发一个应用程序，用户可以在其中与其他用户聊天（1对1，而不是群聊）。我有一个MySQL表，用于存储来自每个用户的所有消息，例如：
from_id to_id message time abc123 def456 Hello 789 def456 abc123 What's up? 1234` def456 abc123 How was last night? 2345 abc123 p0tat0 I missed the bus 3456 def456 p0tat0 I hate you :( 4567` def456 another_user I hate Potato! 5678`如何从AND获取最新消息，
abc123从最新到最旧排序，例如：
from_id to_id message time
abc123 p0tat0 I missed the bus 3456
def456 abc123 How was last night? 2345
time如果重要的话，在消息表中将始终以升序排列。任何帮助将不胜感激。谢谢^。^
SELECT *,'from' as directionFROM messages WHERE from_username='admin' AND 'time' = ( SELECT MAX('time') FROM messages WHERE from_username='admin'OR to_username='admin')
UNION ALL
SELECT *,'to' as directionFROM messages WHERE to_username='admin' AND 'time' = ( SELECT MAX('time') FROM messages WHEREto_username='admin' ORto_username='admin' )
from_id to_id message time
abc123 def456 Hello 789
def456 abc123 What's up? 1234`
def456 abc123 How was last night? 2345
abc123 p0tat0 I missed the bus 3456
def456 p0tat0 I hate you :( 4567`
def456 another_user I hate Potato! 5678`
我正在开发一个应用程序，用户可以在其中与其他用户聊天（1对1，而不是群聊）。我有一个MySQL表，用于存储来自每个用户的所有消息，例如：
如何从AND获取最新消息，abc123从最新到最旧排序，例如：
from_id to_id message time
abc123 p0tat0 I missed the bus 3456
def456 abc123 How was last night? 2345
time 如果重要的话，在消息表中将始终以升序排列。
任何帮助将不胜感激。谢谢^。^
SELECT *, 'from' as directionFROM messages WHERE
from_username='admin' AND 'time' = ( SELECT MAX('time') FROM messages WHERE
from_username='admin' OR to_username='admin')
UNION ALL
SELECT *, 'to' as directionFROM messages WHERE to_username='admin'
AND 'time' = ( SELECT MAX('time') FROM messages WHERE to_username='admin'
ORto_username='admin' )
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