如何没有重复的值

I’m making private messages in my website. Everything is okay but I can’t get the list of all the messages that the user sent or received. I have 2 tables. users(id,username,etc..) and messages (id,user1,user2,message,date)

I’ve tried following to get all list messages for one user

(SELECT DISTINCT * from users WHERE user1 = $userid OR user2 = $userid ORDER BY date ASC)

but I can’t get the messages and I see duplicate values like

User1 User2

2            1

1            2

I want to get just one value for one relation

I'm not sure I understand your question fully, but from my interpretation I think this may help remove duplicate rows for each relationship:

SELECT DISTINCT * FROM messages GROUP BY user1,user2

It’s not working it returns

User1 User2

2 1

1 2

I don’t want to duplicate value