setting up a friend list in mysql

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天涯浪人
天涯浪人 2021-01-31 12:47

I want to make a friends list in my online game. I am not sure how to set it up or where to start. The add friends and accept friends part I can handle, but I don\'t know how to

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  • 2021-01-31 13:25

    Check out the answers in this other post here on stackoverflow...some simple but great explanations to accomplishing what you need.

    Facebook database design?

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  • 2021-01-31 13:29

    A friendship is essentially a mutual relationship between two people. In database terms it's a many-to-many relationship between two users.

    So what you need is a linking table that holds references to two users by ID.

    Example

    Users table

    ID    Username
    1     Bob
    2     Jim
    3     Alice
    

    Friends table

    user1    user2
    1        2
    2        3
    

    This would make Bob friends Jim and Jim friends with Alice.

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  • 2021-01-31 13:30

    An alternative would be to set column A as follow: $checkfriend = (($friend1 $friend2) || ($friend2 $friend1))

    Column B as follow: (friendship accepted or friendship rejected) based on user's choice

    Basically have both user1 and user2 in the same column.

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  • 2021-01-31 13:39

    If your friendship relationship is symmetrical, you can either store each pair in a separate record:

    friend1 friend2
    A       B
    B       A
    A       C
    B       D
    C       B
    D       B
    

    and query all B's friends like that:

    SELECT  friend2
    FROM    friends
    WHERE   friend1 = 'B'
    

    or store the user with the least id in the first field and that with the greatest id in the second one:

    friend1  friend2
    A        B
    A        C
    B        D
    

    and query B's friends like that:

    SELECT  friend1
    FROM    friends
    WHERE   friend2 = 'B'
    UNION ALL
    SELECT  friend2
    FROM    friends
    WHERE   friend1 = 'B'
    

    The first option is a little bit more efficient in MySQL, and this is the only option if your friendship relationship is not symmetrical (like on LiveJournal)

    See this article:

    • Selecting friends
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