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I'm fairly new to PHP and SQL. I have spent today programming a friend system (almost identical to Facebook's) but I am unsure of how I would have multiple friends in the same column. So lets say the user 'admin' has a friend called 'john' admin sends test a request and john accepts, they both go into each others friends column. But lets say another of admin friends sends him a request and he accepts it will simply overwrite 'john' with the new name, therefore only having one value in the column instead of john, another friend, etc. How would it be possible to not overwrite, but instead keep adding to the column.

I hope this makes sense and thanks in advance!

iphoneapplelover123
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  • *multiple friends in the same column*. That's not how Facebook does it. Please read up on [normalization](http://en.wikipedia.org/wiki/Database_normalization). – Kermit Jan 18 '13 at 19:32
  • FB has a one-to-many relationship. They have a `users` table and then, say, a `user_friends` table with two columns: user1id | user2id. Very crude example. But it is most certainly not storing all the friends in a single column in the `users` table. – Eli Gassert Jan 18 '13 at 19:32
  • Ok, thanks for the read. Eli, how would I go about doing this?! Thanks – iphoneapplelover123 Jan 18 '13 at 19:36

1 Answers1

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What you need is a "One to Many" relationship. One 'person' can be friends with many other 'persons'.

You would have one table called person:

person_id | person_name
-----------------------
1 | John
2 | Frank
3 | Mary
4 | Oscar

And you would have a one-to-many table called friends:

person_id1 | person_id2
-----------------------------------
 1 | 2
 1 | 3
 2 | 3

So, now by looking in our friends table. Our first relationship is between John and Frank, they are friends. So is John and Mary, and Frank and Mary. Oscar has no friends.

Blaise Swanwick
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  • `friend_id` is unnecessary. You create a composite primary key of `person_id1` and `person_id2` to prevent duplicate "friendships" – Kermit Jan 18 '13 at 19:37