dpl9717
dpl9717
2014-05-22 08:30

表有3个分离度

已采纳

I'm looking for a query to create a table in MySQL with the degree of seperation between two users. I already found Degrees of Separation Query.But that will, if i understand correctly, result in a recommended friendlist with mutual friends. What i'm looking for is slightly different.

I have a table with "friends" between users (contains no duplicate relations like 1 to 2 & 2 to 1).

friends (id, initiator_user_id, friend_user_id, is_confirmed)

What i am trying to create is a table with all relations between friends, friends of friends and FoFoF. like this:

relation_degrees (id, first_user_id, second_user_id, relation_degree)

so the relation_degree column only contains the value 1 (friends), 2 (FoF) and 3 (FoFoF).

I was able to do it in Excel, but there my friends where stored in a matrix, which make calculations IMO a little bit easier. I hope somebody will be able to give me a hint to do the same in MySQL.

Thanks!!


edit: with the help from Fluffeh i found the following solution to my problem.

  1. i stored the relations in both directions( like 1-2 & 2-1, so without the confirmation column) in table called degree_one
  2. Then i used the query for degree one and two from fluffeh to make table with first & second degree relations. I added a WHERE user <> Friend statement to filter the relations (i guess this is one of the reasons why the query from fluffeh for the third degree relations isn't working correctly)
   `Create table degree_two
   select
   mb.user as User,
   mb.friend as Friend,
   min(mb.rel)  as relation_degree

from ( select 1 as rel, fr1.User, fr1.Friend from degree_one fr1

          union all

      select
          2 as rel,
           fr2.User,
           fr3.Friend
       from
           degree_one fr2
               left outer join degree_one fr3
                   on fr2.Friend=fr3.User


                ) mb

   Where user <> friend



 group by
      mb.User,
      mb.Friend
  1. Then i used this table to do almost the same query. the select statement is on the degree_two table but the outer join is still from the degree_one table.
   Create table degree_three
    select
        mb.user as User,
        mb.friend as Friend,
        min(mb.relation_degree)  as relation_degree
    from
        (
             select
                fr1.relation_degree,
                fr1.User,
                fr1.Friend
            from
                degree_two fr1


          union all

      select
            3 as rel,
            fr2.User,
            fr3.Friend
        from
            degree_two fr2
                left outer join degree_one fr3
                    on fr2.Friend=fr3.User


                ) mb

Where `user` <> `friend`

group by
    mb.User,
    mb.Friend

It is kind of a work around but it gives me the desired output. I'm still wondering why the query from fluffeh doesn't work correctly, because i really want a single query as solution. i will continue fooling around with the query... I hope that somebody can help me merging these query into one.

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2条回答

  • duanquan1243 duanquan1243 7年前

    This query gave me the desired solution result:

    Create table degree_two
    select
        mb.user as User,
        mb.friend as Friend,
        min(mb.rel)  as relation_degree
    from
        (
               select
                1 as rel,
                fr1.User,
                fr1.Friend
            from
                degree_one fr1
    
                union all
    
            select
                2 as rel,
                fr2.User,
                fr3.Friend
            from
                degree_one fr2
                    left outer join degree_one fr3
                        on fr2.Friend=fr3.User
                        where fr2.user <> fr3.friend
    
             union all       
    
             select 
                3 as rel, 
                fr4.user, 
                fr6.Friend
            from 
               (degree_one fr4 
                    left outer join  degree_one fr5 
                        on fr4.friend=fr5.user
                        and fr4.user <> fr5.friend
    
                        left outer join  degree_one fr6
                        on fr5.friend = fr6.user
                       and fr5.user <> fr6.friend)
               where fr6.friend  IS NOT NULL           
    
    
                      ) mb
    
    group by
        mb.User,
        mb.Friend
    

    Thanks Fluffeh for your help!

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  • dongzi5062 dongzi5062 7年前

    You can do this with outer joins back to the table itself...

    select
        mb.initiator_user_id as first_user_id,
        mb.friend_user_id as second_user_id,
        mb.rel as relation_degree
    from
        (
            select
                1 as rel,
                fr1.initiator_user_id,
                fr1.friend_user_id
            from
                friends fr1
    
            union all
    
            select
                2 as rel,
                fr2.initiator_user_id,
                fr3.friend_user_id
            from
                friends fr2
                    left outer join friends fr3
                        on fr2.friend_user_id=fr3.initiator_user_id
            // and again etc or in a code loop (not really done these much)
        ) mb
    

    Basically, it seems you have the IDs able to be linked from friend1 to friend2, but the structure also allows for a query that allows friend1 to use friend2 to see who THEIR friends are - you can union these results with the degree easily enough.

    Edit: Resolving issues based on comment:

    select
        mb.initiator_user_id as first_user_id,
        mb.friend_user_id as second_user_id,
        min(mb.rel)  as relation_degree
    from
        (
            select
                1 as rel,
                fr1.initiator_user_id,
                fr1.friend_user_id
            from
                friends fr1
            where is_confirmed = 1
    
            union all
    
            select
                2 as rel,
                fr2.initiator_user_id,
                fr3.friend_user_id
            from
                friends fr2
                    left outer join friends fr3
                        on fr2.friend_user_id=fr3.initiator_user_id
                        and fr3.is_confirmed = 1
            // and again etc or in a code loop (not really done these much)
        ) mb
    group by
        mb.initiator_user_id,
        mb.friend_user_id
    

    Edit: Adding third layer of relationships based on comment:

    select
        mb.initiator_user_id as first_user_id,
        mb.friend_user_id as second_user_id,
        min(mb.rel)  as relation_degree
    from
        (
            select
                1 as rel,
                fr1.initiator_user_id,
                fr1.friend_user_id
            from
                friends fr1
            where is_confirmed = 1
    
            union all
    
            select
                2 as rel,
                fr2.initiator_user_id,
                fr3.friend_user_id
            from
                friends fr2
                    left outer join friends fr3
                        on fr2.friend_user_id=fr3.initiator_user_id
                        and fr3.is_confirmed = 1
            union all
            select 
                3 as rel, 
                fr4.initiator_user_id, 
                fr5.friend_user_id 
            from 
                friends fr3 
                    left outer join friends fr4 
                        on fr3.friend_user_id=fr4.initiator_user_id 
                        and fr4.is_confirmed = 1
                    left outer join friends fr5
                        on fr4.friend_user_id=fr5.initiator_user_id 
                        and fr5.is_confirmed = 1
            // and again etc or in a code loop (not really done these much)
        ) mb
    group by
        mb.initiator_user_id,
        mb.friend_user_id
    
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